Single step lactide production process with heat recovery

ABSTRACT

The present invention relates to a process for synthesizing lactide, comprising the steps of:
         adding thermal energy to at least one of one or more components;   providing the one or more components to at least one reactor, the one or more components comprising lactic acid and at least one solvent;   converting at least part of the lactic acid into lactide and water;   recovering at least part of the lactide;   recovering at least part of the at least one solvent;   recovering at least part of the thermal energy, wherein at least part of the recovered thermal energy is recovered from the recovered solvent; and   adding the recovered thermal energy to at least one of the one or more components.

CROSS-REFERENCE TO RELATED APPLICATIONS

-   -   This application claims the benefit of PCT/EP2017/065003 filed        Jun. 20, 2017, which claims priority from EP 16175251.4 filed        Jun. 20, 2016, which are incorporated herein by reference in        their entireties for all purposes.

TECHNICAL FIELD

The present invention relates to an industrial process for the singlestep preparation of lactide from lactic acid.

BACKGROUND

Polylactic acid (PLA), a renewable resource mainly obtained from cornstarch and sugar cane, is one of the most important bio-based andbiodegradable plastics, and may replace petroleum based plastics in arange of applications. For the production of PLA, lactic acid (LA) istypically first converted into lactide (LD), its cyclic dimer.Subsequently, this lactide is converted via ring opening polymerizationinto PLA. However, the most costly step is the conversion of lactic acidinto lactide.

Currently, industrial lactide synthesis occurs mainly through a two-stepprocess. A first step in the two-step process is the synthesis of a lowquality lactic acid polymer. A second step is the conversion of thispolymer into lactide via depolymerization, i.e. backbiting. Thistwo-step process is typically energy consuming, selectivity is low, andsignificant amounts of meso-lactide, an undesired lactide, aregenerated. Alternatively, lactide may be synthesized in a gas-phaseprocess over packed solid catalyst beds. Though cheaper than thetwo-step process, this industrial process has limited yield and/orlimited volumetric productivity.

SUMMARY OF THE INVENTION

In view of the above, there is a need in the art to provide analternative industrial process for the preparation of lactide fromlactic acid. There is a need in the art to provide an industrial processfor the preparation of lactide from lactic acid that is cheaper. Thereis a need in the art to provide an industrial process that is optimizedin energy consumption and respects heat integration. There is a need inthe art to provide an industrial process for the preparation of lactidefrom lactic acid that consumes less energy. There is a need in the artto provide an industrial process for the preparation of lactide fromlactic acid that is flexible. There is a need in the art to provide anindustrial process for the preparation of lactide from lactic acid thatis more selective. There is a need in the art to provide an industrialprocess for the preparation of lactide from lactic acid that has highyield. There is a need in the art to provide an industrial process forthe preparation of lactide from lactic acid that has high volumetricproductivity.

There is also a need in the art to provide a single step industrialprocess for the preparation of lactide from lactic acid that is flexibleor independent with regards to the composition of the feed. There isalso a need in the art to provide a single step industrial process forthe preparation of lactide from lactic acid that is flexible thatrequires fewer heaters. There is also a need in the art to provide asingle step industrial process for the preparation of lactide fromlactic acid that has a simpler reactor design. There is also a need inthe art to provide a single step industrial process for the preparationof lactide from lactic acid that has a simpler reactor design. There isalso a need in the art to provide a single step industrial process forthe preparation of lactide from lactic acid that has a smaller slurrypump.

There is also a need in the art to provide a single step industrialprocess for the preparation of lactide from lactic acid that has animproved product yield. There is also a need in the art to provide asingle step industrial process for the preparation of lactide fromlactic acid that has improved overall conversion. There is also a needin the art to provide a single step industrial process for thepreparation of lactide from lactic acid that has independent control ofreactor settings. There is also a need in the art to provide a singlestep industrial process for the preparation of lactide from lactic acidthat can still operate, with catalyst or without catalyst, in case of atechnical malfunction. There is also a need in the art to provide asingle step industrial process for the preparation of lactide fromlactic acid that minimizes solvent. There is also a need in the art toprovide a single step industrial process for the preparation of lactidefrom lactic acid that improves residence time.

There is also a need in the art to provide a single step industrialprocess for the preparation of lactide from lactic acid that is flexibleor independent with regards to the composition of the feed. There isalso a need in the art to provide a single step industrial process forthe preparation of lactide from lactic acid that makes use of residualoligomers. There is also a need in the art to provide a single stepindustrial process for the preparation of lactide from lactic acid thatis flexible or independent with regards to the concentration ofoligomers in the feed. There is also a need in the art to provide asingle step industrial process for the preparation of lactide fromlactic acid that controls the water quantity that enters the reactor(s).There is also a need in the art to provide a single step industrialprocess for the preparation of lactide from lactic acid that controlsthe water quantity that enters the reactor(s). There is also a need inthe art to provide a single step industrial process for the preparationof lactide from lactic acid that is flexible or independent with regardsto the concentration of water in the feed. There is also a need in theart to provide a single step industrial process for the preparation oflactide from lactic acid that is flexible or independent with regards tothe concentration of lactic acid in the feed. There is also a need inthe art to provide a single step industrial process for the preparationof lactide from lactic acid that avoids or limits difficult and/orcostly separation steps, for example for separating a catalyst from thelactic acid, for example by costly techniques such as filtration and/orcentrifugation.

There is also a need in the art to provide a single step industrialprocess for the preparation of lactide from lactic acid that is energyefficient. There is also a need in the art to provide a single stepindustrial process for the preparation of lactide from lactic acid thatavoids or limits the addition of water from an external source. There isalso a need in the art to provide a single step industrial process forthe preparation of lactide from lactic acid that avoids or limits theaddition of catalyst from an external source. There is also a need inthe art to provide a single step industrial process for the preparationof lactide from lactic acid that reduces the cost of a separate catalystregeneration step. There is also a need in the art to provide a singlestep industrial process for the preparation of lactide from lactic acidthat can be operational both with and without catalyst, at littleadditional effort or cost.

There is also a need in the art to provide a single step industrialprocess for the preparation of lactide from lactic acid that is energyefficient. There is also a need in the art to provide a single stepindustrial process for the preparation of lactide from lactic acidwherein the energy input is minimal. There is also a need in the art toprovide a single step industrial process for the preparation of lactidefrom lactic acid wherein the energy loss is minimal.

There is also a need in the art to provide a single step industrialprocess for the preparation of lactide from lactic acid with fewer stepsfor separating water. There is also a need in the art to provide asingle step industrial process for the preparation of lactide fromlactic acid wherein the separation of water is simpler and/or cheaper.There is also a need in the art to provide a single step industrialprocess for the preparation of lactide from lactic acid wherein theseparation of water requires no or less additional heating. There isalso a need in the art to provide a single step industrial process forthe preparation of lactide from lactic acid with no or less degradationof the lactide. There is also a need in the art to provide a single stepindustrial process for the preparation of lactide from lactic acid withno or less degradation of the solvent. There is also a need in the artto provide a single step industrial process for the preparation oflactide from lactic acid wherein the separation of water is compatiblewith the catalyst used. The invention overcomes one or more of theabove-mentioned needs. Preferred embodiments of the invention overcomeone or more of the above-mentioned needs.

In general, the invention provides a process for synthesizing lactide,comprising the steps of: providing one or more components to at leastone reactor, the one or more components comprising lactic acid;converting at least part of the lactic acid into lactide and water,preferably in one step; and recovering at least part of the lactide.

According to a first aspect, the invention provides a process forsynthesizing lactide, preferably an industrial process for synthesizinglactide, comprising the steps of adding thermal energy to at least onesolvent; providing one or more components to at least one reactor, theone or more components comprising lactic acid and the at least onesolvent; converting at least part of the lactic acid into lactide andwater, preferably in one step; and recovering at least part of thelactide; wherein the step of adding thermal energy to the at least onesolvent is performed prior to the step of adding the at least onesolvent to the at least one reactor; and wherein the at least onesolvent is provided in the at least one reactor independently from thelactic acid by a separate entry into the at least one reactor.

According to a second aspect, the invention provides a process forsynthesizing lactide, preferably an industrial process for synthesizinglactide, comprising the steps of providing one or more components to atleast one reactor, the one or more components comprising lactic acid;converting at least part of the lactic acid into lactide and water andinto lactic acid oligomers, preferably in one step; recovering at leastpart of the lactide; recovering at least part of the water and at leastpart of the lactic acid oligomers; adding a feed, optionally comprisinglactic acid oligomers, and optionally comprising water, to the recoveredwater and the recovered lactic acid oligomers, and mixing the feed withthe recovered water and the recovered lactic acid oligomers to form amixture; converting at least part of the lactic acid oligomers in themixture into lactic acid and into lactic acid dimer, preferably in onestep; and removing at least part of the water from the mixture; wherebyat least part of the remainder of the mixture is provided as one of theone or more components that are provided to the at least one reactor.

According to a third aspect, the invention provides a process forsynthesizing lactide, preferably an industrial process for synthesizinglactide, comprising the steps of: adding thermal energy to at least oneof one or more components; providing the one or more components to atleast one reactor, the one or more components comprising lactic acid;converting at least part of the lactic acid into lactide and water,preferably in one step; recovering at least part of the lactide;recovering at least part of the thermal energy; and adding the recoveredthermal energy to at least one of the one or more components.

According to a fourth aspect, the invention provides a process forsynthesizing lactide, preferably an industrial process for synthesizinglactide, comprising the steps of: providing one or more components to atleast one reactor, the one or more components comprising lactic acid;converting at least part of the lactic acid into lactide and water,preferably in one step; recovering at least part of the lactide; andrecovering at least part of the water; wherein the step of recovering atleast part of the water comprises a decantation step, preferably withthe proviso that the step of recovering at least part of the water doesnot comprise an azeotropic distillation step.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, composed of FIG. 1A, FIG. 1B, FIG. 1C, and FIG. 1D, representsflow diagram of a process, combining several preferred embodiments ofthe present invention.

Following reference numbers are adhered to in FIG. 1: Original feed(100); Pumps (101,102,103,104), for example vacuum pump (104); Lacticacid, LA (110); Lactic acid dimer, L2A (120); Lactic acid oligomers,L3A, L4A, LxA (130); Water (140); Solvent (150); Catalyst system (160);Lactide (200); Lactide filter (210); Valve for lactide purification(215); Lactide purifier (220); Refrigeration cycle for lactidecrystallization (300); First crystallization reactor (301); Secondcrystallization reactor (302); Compressor (310); Heat exchangers forrefrigeration cycle (311, 312); Valve for refrigeration cycle (315);High quality water (400); Water separation between reactors (410);Decantation step (420); Water separation membrane (430); Steam generator(500); Optional heat exchanger for steam/feed (510); Heated steam forfeed (511); Cooled steam from feed (512); Heat exchanger forsteam/solvent (520); Heated steam for solvent (521); Cooled steam fromsolvent (522); First heat recovery step (610); Cold stream and hotstream sides of heat exchanger for first heat recovery step (611, 612);Second heat recovery step (620); Cold stream and hot stream sides ofheat exchanger for second heat recovery step (621, 622); Third heatrecovery step (630); Heat exchanger for third heat recovery step (632);First reactor (710); Second reactor (720); Optional recycling reactor oroptional regeneration reactor (730)

FIG. 2 illustrates a semi-batch catalyst injection system which may beused in the present invention, comprising: (1) a regenerated catalystslurry inlet from a centrifugal separator; (2) a catalyst slurry outletinto the reactor; (3) a gas inlet to build up pressure; and (21,22)valves.

FIG. 3 composed of FIG. 3A, FIG. 3B, and FIG. 3C, illustrates possiblereactor configurations to include in situ water separation and heatrecovery. FIG. 3B illustrates the use of two condensation steps: thefirst vessel operates at a temperature below the boiling point of thesolvent (but higher than the boiling point of water) to recover mostlythe solvent, white the second vessel operates at a temperature below theboiling point of water to recover water and remaining trace of solventwhich is sent back into the reactor. FIG. 3C illustrates an in situseparation of solvent, which is implanted inside the reactor by addingsome distillation steps to separate solvent and return it back into thereactor.

FIG. 4 represents a flow diagram of a process, combining severalpreferred embodiments of the present invention.

FIG. 5 represents a flow diagram of a process suitable to producelactide, using distillation in the purification steps.

FIG. 6 shows the regeneration in water of 45° C. of a solid catalystsuitable to be used in the formation of lactide in some embodiments ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

Before the present processes according to the present invention aredescribed, it is to be understood that this invention is not limited toparticular processes described, since such processes may, of course,vary. It is also to be understood that the terminology used herein isnot intended to be limiting, since the scope of the present inventionwill be limited only by the appended claims.

When describing the invention, the terms used are to be construed inaccordance with the following definitions, unless the context dictatesotherwise.

As used herein, the singular forms “a”, “an”, and “the” include bothsingular and plural referents unless the context clearly dictatesotherwise. By way of example, “a resin” means one resin or more than oneresin. Reference throughout this specification to “one embodiment” or“an embodiment” means that a particular feature, structure orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. Thus, appearancesof the phrases “in one embodiment” or “in an embodiment” in variousplaces throughout this specification are not necessarily all referringto the same embodiment, but may. Furthermore, the particular features,structures or characteristics may be combined in any suitable manner, aswould be apparent to a person skilled in the art from this disclosure,in one or more embodiments. Furthermore, while some embodimentsdescribed herein include some but not other features included in otherembodiments, combinations of features of different embodiments are meantto be within the scope of the invention, and form different embodiments,as would be understood by those in the art. For example, in thefollowing claims, any of the claimed embodiments can be used in anycombination. The terms “comprising”, “comprises” and “comprised of” asused herein are synonymous with “including”, “includes” or “containing”,“contains”, and are inclusive or open-ended and do not excludeadditional, non-recited members, elements or method steps. It will beappreciated that the terms “comprising”, “comprises” and “comprised of”as used herein comprise the terms “consisting of”, “consists” and“consists of”. The recitation of numerical ranges by endpoints includesall integer numbers and, where appropriate, fractions subsumed withinthat range (e.g. 1 to 5 can include 1, 2, 3, 4 when referring to, forexample, a number of elements, and can also include 1.5, 2, 2.75 and3.80, when referring to, for example, measurements). The recitation ofend points also includes the end point values themselves (e.g. from 1.0to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein isintended to include all sub-ranges subsumed therein.

All references cited in the present specification are herebyincorporated by reference in their entirety. In particular, theteachings of all references herein specifically referred to areincorporated by reference.

Preferred statements (features) and embodiments of the processes anduses of this invention are set herein below. Each statements andembodiments of the invention so defined may be combined with any otherstatement and/or embodiments unless clearly indicated to the contrary.In particular, any feature indicated as being preferred or advantageousmay be combined with any other feature or features or statementsindicated as being preferred or advantageous. Hereto, the presentinvention is in particular captured by any one or any combination of oneor more of the below numbered aspects and embodiments 1 to 139, with anyother statement and/or embodiments.

-   1. Process for synthesizing lactide, preferably an industrial    process for synthesizing lactide, comprising the steps of: providing    one or more components to at least one reactor, the one or more    components comprising lactic acid; converting at least part of the    lactic acid into lactide and water, preferably in one step; and    recovering at least part of the lactide.-   2. Process for synthesizing lactide, preferably an industrial    process for synthesizing lactide, comprising the steps of: adding    thermal energy to at least one solvent; providing one or more    components to at least one reactor, the one or more components    comprising lactic acid and the at least one solvent; converting at    least part of the lactic acid into lactide and water, preferably in    one step; and recovering at least part of the lactide; wherein the    step of adding thermal energy to the at least one solvent is    performed prior to the step of adding the at least one solvent to    the at least one reactor; and wherein the at least one solvent is    provided in the at least one reactor independently from the lactic    acid by a separate entry into the at least one reactor; preferably    wherein the step of converting at least part of the lactic acid into    lactide and water is performed in one step.-   3. Process for synthesizing lactide, preferably an industrial    process for synthesizing lactide, comprising the steps of: providing    one or more components to at least one reactor, the one or more    components comprising lactic acid; converting at least part of the    lactic acid into lactide and water and into lactic acid oligomers,    preferably in one step; recovering at least part of the lactide;    recovering at least part of the water and at least part of the    lactic acid oligomers; adding a feed, optionally comprising lactic    acid oligomers, and optionally comprising water, to the recovered    water and the recovered lactic acid oligomers, and mixing the feed    with the recovered water and the recovered lactic acid oligomers to    form a mixture; converting at least part of the lactic acid    oligomers in the mixture into lactic acid and into lactic acid    dimer, preferably in one step; and removing at least part of the    water from the mixture; whereby at least part of the remainder of    the mixture is provided as one of the one or more components that    are provided to the at least one reactor; preferably wherein the    step of converting at least part of the lactic acid into lactide and    water is performed in one step.-   4. Process for synthesizing lactide, preferably an industrial    process for synthesizing lactide, comprising the steps of: adding    thermal energy to at least one of one or more components; providing    the one or more components to at least one reactor, the one or more    components comprising lactic acid and preferably at least one    solvent; converting at least part of the lactic acid into lactide    and water, preferably in one step; recovering at least part of the    lactide; preferably recovering at least part of the at least one    solvent; recovering at least part of the thermal energy, preferably    wherein at least part of the recovered thermal energy is recovered    from the recovered solvent; and adding the recovered thermal energy    to at least one of the one or more components, preferably in the    first and/or second listed step.-   5. Process for synthesizing lactide, preferably an industrial    process for synthesizing lactide, comprising the steps of: providing    one or more components to at least one reactor, the one or more    components comprising lactic acid and preferably a solvent;    converting at least part of the lactic acid into lactide and water,    preferably in one step; recovering at least part of the lactide; and    recovering at least part of the water; preferably wherein the step    of converting at least part of the lactic acid into lactide and    water is performed in one step; and wherein the step of recovering    at least part of the water comprises a decantation step, preferably    with the proviso that the step of recovering at least part of the    water does not comprise an azeotropic distillation step.-   6. Process for synthesizing lactide, preferably an industrial    process for synthesizing lactide, comprising the steps of providing    one or more components to at least one reactor, the one or more    components comprising lactic acid and at least one solvent;    converting at least part of the lactic acid into lactide and water,    preferably in one step; and recovering at least part of the lactide;    wherein the at least one solvent is provided in the at least one    reactor independently from the lactic acid by a separate entry into    the at least one reactor.-   7. Process for synthesizing lactide, preferably an industrial    process for synthesizing lactide, comprising the steps of: adding    thermal energy to at least one solvent; providing one or more    components to at least one reactor, the one or more components    comprising lactic acid and the at least one solvent; converting at    least part of the lactic acid into lactide and water, preferably in    one step; and recovering at least part of the lactide: wherein the    step of adding thermal energy to the at least one solvent is    performed prior to the step of adding the at least one solvent to    the at least one reactor.-   8. Process for synthesizing lactide, preferably an industrial    process for synthesizing lactide, comprising the steps of providing    one or more components to at least two reactors, preferably to at    least two reactors connected in series, the one or more components    comprising lactic acid; converting at least part of the lactic acid    into lactide and water, preferably in one step; and recovering at    least part of the lactide.-   9. Process for synthesizing lactide, preferably an industrial    process for synthesizing lactide, comprising the steps of: providing    one or more components to at least two reactors, preferably to at    least two reactors connected in series, the one or more components    comprising lactic acid and at least one solvent; converting at least    part of the lactic acid into lactide and water, preferably in one    step; and recovering at least part of the lactide; wherein the at    least one solvent is divided into at least two solvent fractions,    and wherein each solvent fraction is separately provided to each    reactor of the at least two reactors.-   10. Process for synthesizing lactide, preferably an industrial    process for synthesizing lactide, comprising the steps of providing    one or more components to at least one reactor, the one or more    components comprising lactic acid and at least one catalyst system;    converting at least part of the lactic acid into lactide and water,    preferably in one step; recovering at least part of the lactide;    recovering at least part of the at least part of the water,    optionally wherein the recovered water comprises at least part of at    least one catalyst system; recovering at least part of the at least    one catalyst system, optionally wherein the recovered catalyst    system is comprised in at least part of the water, and regenerating    at least part of the recovered catalyst system; wherein the step of    regenerating at least part of the recovered catalyst system is    performed through hydrolysis by the recovered water.-   11. Process for synthesizing lactide, preferably an industrial    process for synthesizing lactide, comprising the steps of: providing    one or more components to at least one reactor, the one or more    components comprising lactic acid; converting at least part of the    lactic acid into lactide and water, preferably in one step; and    recovering at least part of the lactide; wherein the step of    recovering at least part of the lactide comprises a first    crystallization step and a second crystallization step.-   12. Process for synthesizing lactide, preferably an industrial    process for synthesizing lactide, comprising the steps of: providing    one or more components to at least one reactor, the one or more    components comprising lactic acid; converting at least part of the    lactic acid into lactide and water, preferably in one step;    recovering at least part of the lactide; and recovering at least    part of the water, wherein the step of recovering at least part of    the water comprises a decantation step preferably with the proviso    that the step of recovering at least part of the water does not    comprise an azeotropic distillation step.-   13. Process for synthesizing lactide, preferably an industrial    process for synthesizing lactide, comprising the steps of: providing    one or more components to at least one reactor, the one or more    components comprising lactic acid; converting at least part of the    lactic acid into lactide and water, preferably in one step;    recovering at least part of the lactide; and purifying the recovered    lactide; preferably wherein the step of purifying the recovered    lactide comprises a combination of vacuum and heating, and/or    wherein the step of purifying the recovered lactide comprises a    purifying crystallization step.-   14. Process according any one of the preceding statements, wherein    the step of converting at least part of the lactic acid into lactide    and water is performed in one step.-   15. Process according to any one of the preceding statements,    wherein the one or more components comprise at least one solvent.-   16. Process according to any one of the preceding statements,    wherein the one or more components comprise at least one catalyst    system.-   17. Process according to any one of the preceding statements,    comprising the step of: recovering at least part of the water,    optionally wherein the recovered water comprises at least part of    the at least one catalyst system.-   18. Process according to any one of the preceding statements,    comprising the step of: recovering at least part of the at least one    catalyst system, optionally wherein the recovered catalyst system is    comprised in at least part of the water.-   19. Process according to any one of the preceding statements,    comprising the step of: recovering at least part of the water and at    least part of the at least one catalyst system, wherein the    recovered water comprises at least part of the at least one catalyst    system.-   20. Process according to any one of the preceding statements,    comprising the step of: recovering at least part of the at least one    solvent.-   21. Process according to any one of the preceding statements,    comprising the step of: converting at least part of the lactic acid    into lactide and water and into lactic acid oligomers, preferably in    one step; and recovering at least part of the lactic acid oligomers.-   22. Process according to any one of the preceding statements,    comprising the step of: adding thermal energy to at least one of the    one or more components.-   23. Process according to any one of the preceding statements,    wherein the step of adding thermal energy to at least one of the one    or more components is performed prior to the step of adding the one    or more components to the at least one reactor.-   24. Process according to any one of the preceding statements,    comprising the step of: recovering thermal energy from at least one    of the one or more recovered components.-   25. Process according to any one of the preceding statements,    comprising the step of: providing the one or more components to at    least two reactors, preferably to at least two reactors connected in    series.-   26. Process according to any one of the preceding statements,    comprising the steps of: adding thermal energy to at least one    solvent; providing one or more components to at least one reactor,    the one or more components comprising lactic acid and the at least    one solvent; converting at least part of the lactic acid into    lactide and water, preferably in one step; and recovering at least    part of the lactide; wherein the step of adding thermal energy to    the at least one solvent is performed prior to the step of adding    the at least one solvent to the at least one reactor; and wherein    the at least one solvent is provided in the at least one reactor    independently from the lactic acid by a separate entry into the at    least one reactor.-   27. Process according to any one of the preceding statements,    comprising the steps of: providing one or more components to at    least one reactor, the one or more components comprising lactic    acid; converting at least part of the lactic acid into lactide and    water and into lactic acid oligomers, preferably in one step;    recovering at least part of the lactide; recovering at least part of    the water and at least part of the lactic acid oligomers; adding a    feed, optionally comprising lactic acid oligomers, and optionally    comprising water, to the recovered water and the recovered lactic    acid oligomers, and mixing the feed with the recovered water and the    recovered lactic acid oligomers to form a mixture; converting at    least part of the lactic acid oligomers in the mixture into lactic    acid and into lactic acid dimer, preferably in one step; and    removing at least part of the water from the mixture; whereby at    least part of the remainder of the mixture is provided as one of the    one or more components that are provided to the at least one    reactor.-   28. Process according to any one of the preceding statements,    comprising the steps of adding thermal energy to at least one of one    or more components; providing the one or more components to at least    one reactor, the one or more components comprising lactic acid;    converting at least part of the lactic acid into lactide and water,    preferably in one step; recovering at least part of the lactide;    recovering at least part of the thermal energy; and adding the    recovered thermal energy to at least one of the one or more    components.-   29. Process according to any one of the preceding statements,    comprising the steps of: providing one or more components to at    least one reactor, the one or more components comprising lactic    acid; converting at least part of the lactic acid into lactide and    water, preferably in one step; recovering at least part of the    lactide; and recovering at least part of the water, wherein the step    of recovering at least part of the water comprises a decantation    step, preferably with the proviso that the step of recovering at    least part of the water does not comprise an azeotropic distillation    step.-   30. Process according to any one of the preceding statements,    comprising the steps of: providing one or more components to at    least one reactor, the one or more components comprising lactic acid    and at least one solvent; converting at least part of the lactic    acid into lactide and water, preferably in one step; and recovering    at least part of the lactide; wherein the at least one solvent is    provided in the at least one reactor independently from the lactic    acid by a separate entry into the at least one reactor.-   31. Process according to any one of the preceding statements,    comprising the steps of: adding thermal energy to at least one    solvent; providing one or more components to at least one reactor,    the one or more components comprising lactic acid and the at least    one solvent; converting at least part of the lactic acid into    lactide and water, preferably in one step; and recovering at least    part of the lactide; wherein the step of adding thermal energy to    the at least one solvent is performed prior to the step of adding    the at least one solvent to the at least one reactor.-   32. Process according to any one of the preceding statements,    comprising the steps of: providing one or more components to at    least two reactors, preferably to at least two reactors connected in    series, the one or more components comprising lactic acid;    converting at least part of the lactic acid into lactide and water,    preferably in one step; and recovering at least part of the lactide.-   33. Process according to any one of the preceding statements,    comprising the steps of: providing one or more components to at    least two reactors, preferably to at least two reactors connected in    series, the one or more components comprising lactic acid and at    least one solvent; converting at least part of the lactic acid into    lactide and water, preferably in one step; and recovering at least    part of the lactide; wherein the at least one solvent is divided    into at least two solvent fractions, and wherein each solvent    fraction is separately provided to each reactor of the at least two    reactors.-   34. Process according to any one of the preceding statements,    comprising the steps of: providing one or more components to at    least one reactor, the one or more components comprising lactic acid    and at least one catalyst system; converting at least part of the    lactic acid into lactide and water, preferably in one step;    recovering at least part of the lactide; recovering at least part of    the at least part of the water, optionally wherein the recovered    water comprises at least part of at least one catalyst system;    recovering at least part of the at least one catalyst system,    optionally wherein the recovered catalyst system is comprised in at    least part of the water and regenerating at least part of the    recovered catalyst system; wherein the step of regenerating at least    part of the recovered catalyst system is performed through    hydrolysis by the recovered water.-   35. Process according to any one of the preceding statements,    comprising the steps of: providing one or more components to at    least one reactor, the one or more components comprising lactic    acid; converting at least part of the lactic acid into lactide and    water, preferably in one step; and recovering at least part of the    lactide; wherein the step of recovering at least part of the lactide    comprises a first crystallization step and a second crystallization    step.-   36. Process according to any one of the preceding statements,    comprising the steps of: providing one or more components to at    least one reactor, the one or more components comprising lactic    acid; converting at least part of the lactic acid into lactide and    water, preferably in one step; recovering at least part of the    lactide; and recovering at least part of the water, wherein the step    of recovering at least part of the water comprises a decantation    step with the proviso that the step of recovering at least part of    the water does not comprise an azeotropic distillation step.-   37. Process according to any one of the preceding statements,    comprising the steps of: providing one or more components to at    least one reactor, the one or more components comprising lactic    acid; converting at least part of the lactic acid into lactide and    water, preferably in one step; recovering at least part of the    lactide; and purifying the recovered lactide; preferably wherein the    step of purifying the recovered lactide comprises a combination of    vacuum and heating, and/or wherein the step of purifying the    recovered lactide comprises a purifying crystallization step.-   38. Process according to any one of the preceding statements,    wherein prior to the step of adding the at least one solvent to the    at least one reactor, the solvent has a temperature of at least    140° C. and at most 300° C.; preferably of at least 150° C. and at    most 250° C.; preferably of at least 160° C. and at most 220° C.-   39. Process according to any one of the preceding statements,    wherein prior to the step of adding the at least one solvent to the    at least one reactor, the solvent has a temperature of at least    5° C. greater than the temperature of the lactic acid, preferably of    at least 10° C. greater than the temperature of the lactic acid,    preferably of at least 20° C. greater than the temperature of the    lactic acid, preferably of at least 30° C. greater than the    temperature of the lactic acid, preferably of at least 40° C.    greater than the temperature of the lactic acid, preferably of at    least 50° C. greater than the temperature of the lactic acid,    preferably of at least 60° C. greater than the temperature of the    lactic acid, preferably of at least 70° C. greater than the    temperature of the lactic acid, preferably of at least 80° C.    greater than the temperature of the lactic acid.-   40. Process according to any one of the preceding statements,    wherein prior to the step of adding the at least one solvent to the    at least one reactor, the solvent has a temperature of at least    5° C. and at most 100° C. greater than the temperature of the lactic    acid, preferably of at least 10° C. and at most 80° C. greater, and    preferably of at least 15° C. and at most 50° C. greater.-   41. Process according to any one of the preceding statements,    wherein the one or more components are provided to at least two    reactors, preferably to at least two reactors connected in series.-   42. Process according to any one of the preceding statements,    comprising the step of recovering at least part of the water,    wherein the at least part of the water is recovered between the at    least two reactors.-   43. Process according to any one of the preceding statements,    wherein at least 50% of the water is recovered between the at least    two reactors, based on the total amount of water exiting the first    reactor of the at least two reactors.-   44. Process according to any one of the preceding statements,    wherein the at least one solvent is divided into at least two    solvent fractions, and wherein each solvent fraction is separately    provided to each reactor of the at least two reactors.-   45. Process according to any one of the preceding statements,    wherein the at least two solvent fractions comprise a first solvent    fraction and a second solvent fraction, and wherein at least part of    the thermal energy is added to the first solvent fraction.-   46. Process according to any one of the preceding statements,    wherein the at least two solvent fractions comprise a first solvent    fraction and a second solvent fraction, and wherein at least part of    the thermal energy is added to the second solvent fraction.-   47. Process according to any one of the preceding statements,    comprising the steps of: providing a first solvent fraction    comprising at least 50% and at most 100% of the at least one    solvent, preferably at least 60% and at most 85% of the at least one    solvent, to the first reactor of the at least two reactors; and    providing a second solvent fraction comprising at least 0% and at    most 50% of the at least one solvent, preferably at least 15% and at    most 40% of the at least one solvent, to the second reactor of the    at least two reactors; with % based on the total sum weight of the    first solvent fraction and the second solvent fraction.-   48. Process according to any one of the preceding statements,    wherein the thermal energy added to the at least one solvent is at    least partly recovered thermal energy, preferably wherein the partly    recovered thermal energy was recovered from recovered solvent and/or    recovered water.-   49. Process according to any one of the preceding statements,    wherein the one or more components provided to the at least one    reactor comprises at least 1% by weight of lactic acid and at most    100% by weight of lactic acid, with % by weight based on the total    weight of the one or more components, preferably at least 5% by    weight and at most 95% by weight, preferably at least 15% by weight    and at most 90% by weight.-   50. Process according to any one of the preceding statements,    wherein the step of converting at least part of the lactic acid    oligomers in the mixture into lactic acid and into lactic acid dimer    is performed through hydrolysis by the recovered water and/or    through hydrolysis by water present in the feed.-   51. Process according to any one of the preceding statements,    wherein the one or more components comprise at least one catalyst    system, and wherein the process comprises the steps of: providing at    least one catalyst system to the at least one reactor; recovering at    least part of the at least one catalyst system; and regenerating at    least part of the recovered catalyst system.-   52. Process according to any one of the preceding statements,    wherein the step of regenerating at least part of the recovered    catalyst system is performed through hydrolysis by the recovered    water and/or through hydrolysis by water present in the feed.-   53. Process according to any one of the preceding statements,    wherein the at least one catalyst system is regenerated in-line with    the at least one reactor.-   54. Process according to any one of the preceding statements,    wherein the at least one catalyst system comprises an acidic    zeolite, preferably H-BEA.-   55. Process according to any one of the preceding statements,    wherein the step of removing at least part of the water from the    mixture is performed with a membrane.-   56. Process according to any one of the preceding statements,    wherein the feed comprises lactic acid oligomers.-   57. Process according to any one of the preceding statements,    wherein the feed comprises at least 1% by weight lactic acid    oligomers and at most 20% by weight lactic acid oligomers;    preferably at least 5% by weight lactic acid oligomers and at most    15% by weight lactic acid oligomers; preferably about 10% by weight    lactic acid oligomers; with % by weight compared to the total weight    of lactic acid, lactic acid dimer, and lactic acid oligomers    combined.-   58. Process according to any one of the preceding statements,    wherein the step of converting at least part of the lactic acid    oligomers in the mixture into lactic acid and into lactic acid    dimer, and optionally the step of regenerating at least part of the    recovered catalyst system, is performed in one or more recycling    pipes.-   59. Process according to any one of the preceding statements,    comprising the step of recovering at least part of the water;    wherein at least part of the recovered thermal energy is recovered    from the recovered water.-   60. Process according to any one of the preceding statements,    wherein the one or more components comprise at least one solvent,    comprising the step of recovering at least part of the at least one    solvent; wherein at least part of the recovered thermal energy is    recovered from the recovered solvent.-   61. Process according to any one of the preceding statements,    wherein at least part of the recovered thermal energy is recovered    from the recovered lactide.-   62. Process to according to any one of the preceding statements,    wherein the step of recovering at least part of the lactide    comprises a first crystallization step and a second crystallization    step.-   63. Process according to any one of the preceding statements,    wherein the first crystallization step and the second    crystallization step are each independently cooled.-   64. Process according to any one of the preceding statements,    wherein the step of recovering at least part of the thermal energy    is performed during the first crystallization step.-   65. Process according to any one of the preceding statements,    wherein the step of recovering at least part of the thermal energy    is performed during the second crystallization step.-   66. Process according to any one of the preceding statements,    wherein at least part of the recovered thermal energy is added to    the lactic acid.-   67. Process according to any one of the preceding statements,    wherein the one or more components comprise at least one solvent,    and wherein at least part of the recovered thermal energy is added    to the solvent-   68. Process according to any one of the preceding statements,    wherein at least part of the recovered thermal energy is recovered    from the recovered water, and wherein at least part of the recovered    thermal energy is added to the lactic acid.-   69. Process according to any one of the preceding statements,    wherein at least part of the recovered thermal energy is recovered    from the recovered water, and wherein at least part of the recovered    thermal energy is added to the solvent.-   70. Process according to any one of the preceding statements,    wherein at least part of the recovered thermal energy is recovered    from the recovered solvent, and wherein at least part of the    recovered thermal energy is added to the lactic acid.-   71. Process according to any one of the preceding statements,    wherein at least part of the recovered thermal energy is recovered    from the recovered solvent, and wherein at least part of the    recovered thermal energy is added to the solvent-   72. Process according to any one of the preceding statements,    wherein at least part of the recovered thermal energy is recovered    from the recovered lactide, and wherein at least part of the    recovered thermal energy is added to the lactic acid.-   73. Process according to any one of the preceding statements,    wherein at least part of the recovered thermal energy is recovered    from the recovered lactide, and wherein at least part of the    recovered thermal energy is added to the solvent-   74. Process according to any one of the preceding statements,    wherein at least part of the recovered thermal energy is recovered    from the recovered water, wherein at least part of the recovered    thermal energy is recovered from the recovered solvent, wherein at    least part of the recovered thermal energy is recovered from the    recovered lactide, and wherein at least part of the recovered    thermal energy is added to the solvent.-   75. Process according to any one of the preceding statements,    wherein the steps of:    -   recovering at least part of the thermal energy, wherein at least        part of the recovered thermal energy is recovered from the        recovered solvent; and    -   adding the recovered thermal energy to at least one of the one        or more components;    -   are performed with a heat exchanger.-   76. Process according to any one of the preceding statements, with    the proviso that the step of recovering at least part of the water    does not comprise a liquid/liquid extraction step.-   77. Process according to any one of the preceding statements,    wherein the one or more components comprise at least one catalyst    system and process comprises the step of: recovering at least part    of the water, wherein the recovered water comprises at least part of    at least one catalyst system.-   78. Process according to any one of the preceding statements,    wherein the at least one catalyst system comprises at least one    acidic zeolite, preferably H-BEA.-   79. Process according to any one of the preceding statements,    comprising the step of: providing one or more components to at least    two reactors, preferably to at least two reactors connected in    series.-   80. Process according to any one of the preceding statements,    wherein the at least part of the water is recovered between the at    least two reactors.-   81. Process according to any one of the preceding statements,    wherein the step of recovering at least part of the lactide is    performed by crystallization, preferably wherein the step of    recovering at least part of the lactide comprises a first    crystallization step and a second crystallization step.-   82. Process according to any one of the preceding statements,    comprising the step of: purifying the recovered lactide.-   83. Process according to any one of the preceding statements,    wherein the step of purifying the recovered lactide comprises a    combination of vacuum and heating.-   84. Process according to any one of the preceding statements,    wherein the step of purifying the recovered lactide is performed at    a pressure of at most 200 mbar, preferably at most 100 mbar, for    example of at least 20 mbar and at most 40 mbar, preferably of about    30 mbar.-   85. Process according to any one of the preceding statements,    wherein the step of purifying the recovered lactide is performed at    a temperature of at most the melting point of lactide, preferably of    at most 90° C., for example of at least 25° C. and at most 90° C.-   86. Process according to any one of the preceding statements,    wherein the step of purifying the recovered lactide comprises a    purifying crystallization step.-   87. Process according to any one of the preceding statements,    wherein the one or more components comprise a solvent that is    non-miscible with water, preferably wherein the solvent is    isobutylbenzene or decane, preferably isobutylbenzene.-   88. Process according to any one of the preceding statements,    wherein the step of converting at least part of the lactic acid into    lactide and water is performed in one step.-   89. Process according to any one of the preceding statements,    wherein the process is an industrial process for synthesizing    lactide.-   90. Process according to any one of the preceding statements,    wherein the process is an industrial process for synthesizing    lactide, and wherein the step of converting at least part of the    lactic acid into lactide and water is performed in one step.-   91. Process according to any one of the preceding statements,    wherein the at least one reactor is a mixed reactor, preferably    wherein the at least one reactor is mixed mechanically and/or with    internal or external fluid flow.-   92. Process according to any one of the preceding statements,    wherein the at least two reactors are mixed reactors, preferably    wherein the at least two reactors are mixed mechanically and/or with    internal or external fluid flow.-   93. Process according to any one of the preceding statements,    wherein the step of adding thermal energy to at least one of the one    or more components is performed after the step of adding the at    least one of the one or more components to the at least one reactor,    for example by an internal exchanger or a jacketed wall.-   94. Process according to any one of the preceding statements,    wherein the step of adding thermal energy to at least one of the one    or more components is performed after the step of adding the at    least one of the one or more components to the at least two    reactors, for example by an internal exchanger or a jacketed wall.-   95. Process according to any one of the preceding statements,    wherein the step of recovering thermal energy is performed after the    last reactor of the at least one reactor or after the last reactor    of the at least two reactors.-   96. Process according to any one of the preceding statements,    wherein the step of recovering thermal energy is performed between    reactors of the at least one reactor or after the last reactor of    the at least two reactors.-   97. Process according to any one of the preceding statements,    wherein the step of recovering thermal energy is performed with a    heat exchanger.-   98. Process according to any one of the preceding statements,    wherein the lactic acid is converted into lactide in a single    reactor.-   99. Process according to any one of the preceding statements,    wherein the lactic acid is independently converted into lactide in    each reactor of the at least two reactors.-   100. Process according to any one of the preceding statements,    comprising the step of recovering the at least one solvent,    preferably comprising the step of recycling the at least one    solvent.-   101. Process according to any one of the preceding statements,    wherein the at least one solvent is a C₅-C₂₄ alkane.-   102. Process according to any one of the preceding statements,    wherein the at least one solvent is decane.-   103. Process according to any one of the preceding statements,    wherein the at least one solvent is an aromatic solvent, preferably    benzene, preferably substituted with one or more C₁-C₄ linear or    branched alkyl groups.-   104. Process according to any one of the preceding statements,    wherein the at least one solvent is cumene, o-xylene,    isobutylbenzene, p-xylene, or toluene, preferably wherein the at    least one solvent is cumene, o-xylene, or isobutylbenzene,    preferably wherein the at least one solvent is isobutylbenzene.-   105. Process according to any one of the preceding statements,    wherein the at least one catalyst system is dispersed in the at    least one reactor in form of a slurry.-   106. Process according to any one of the preceding statements,    comprising the step of recovering the at least one catalyst system,    preferably recycling the at least one catalyst system.-   107. Process according to any one of the preceding statements,    wherein the at least one catalyst system is regenerated by the    solvent.-   108. Process according to any one of the preceding statements,    wherein the at least one catalyst system is regenerated through    calcination.-   109. Process according to any one of the preceding statements,    performed in the absence of any catalyst system.-   110. Process according to any one of the preceding statements,    wherein the process is sometimes performed in the presence of at    least one catalyst system and sometimes performed in the absence of    any catalyst system.-   111. Process according to any one of the preceding statements,    wherein the at least one catalyst system comprises at least one    acidic zeolite.-   112. Process according to any one of the preceding statements,    wherein the at least one catalyst system comprises at least one    acidic zeolite comprising: two or three interconnected and    non-parallel channel systems, wherein at least one of said channel    systems comprises 10- or more-membered ring channels; and a    framework Si/X₂ ratio of at least 24 as measured by NMR; or three    interconnected and non-parallel channel systems, wherein at least    two of said channel systems comprise 10- or more-membered ring    channels; and a framework Si/X₂ ratio of at least 6 as measured by    NMR; wherein each X is Al or B.-   113. Process according to any one of the preceding statements,    wherein at least one of the interconnected and non-parallel channel    systems comprises 12- or more membered ring channels.-   114. Process according to any one of the preceding statements,    wherein the acidic zeolite has a Brønsted acid density between 0.05    and 6.5 mmol/g dry weight.-   115. Process according to any one of the preceding statements,    wherein X is Al.-   116. Process according to any one of the preceding statements,    wherein the acidic zeolite comprises at least three interconnecting    and non-parallel channel systems.-   117. Process according to any one of the preceding statements,    wherein the acidic zeolite comprises a topology selected from the    group comprising BEA, MFI, FAU, MEL, FER, and MWW, preferably BEA.-   118. Process according to any one of the preceding statements,    wherein the at least one catalyst system comprises an acidic    zeolite, preferably wherein the at least one catalyst system    comprises an H-BEA zeolite.-   119. Process according to any one of the preceding statements,    comprising the step of recovering at least part of the water,    optionally wherein the water comprises at least part of the at least    one catalyst system.-   120. Process according to any one of the preceding statements,    wherein the step of recovering at least part of the water comprises    a distillation step.-   121. Process according to any one of the preceding statements,    wherein the step of recovering at least part of the water comprises    a filtration step, preferably membrane filtration, for example    through reverse osmosis.-   122. Process according to any one of the preceding statements,    wherein the step of recovering thermal energy is performed after the    step of recovering at least part of the water.-   123. Process according to any one of the preceding statements,    wherein the lactic acid is obtained by bacterial fermentation of    glucose or sucrose.-   124. Process according to any one of the preceding statements,    wherein the lactic acid is obtained by chemocatalytic transformation    of trioses, hexoses, cellulose, or glycerol.-   125. Process according to any one of the preceding statements,    wherein the lactic acid comprises L-lactic acid.-   126. Process according to any one of the preceding statements,    wherein the lactic acid comprises D-lactic acid.-   127. Process according to any one of the preceding statements,    wherein the one or more components provided to the at least one    reactor comprises at least 3% by weight of water and at most 95% by    weight of water, with % by weight based on the total weight of the    one or more components, preferably at least 5% by weight and at most    50% by weight, with % by weight based on the total weight of the one    or more components provided to the at least one reactor, preferably    at least 10% by weight and at most 30% by weight, with % by weight    based on the total weight of the one or more components provided to    the at least one reactor.-   128. Process according to any one of the preceding statements,    wherein the one or more components provided to the at least one    reactor comprises at least 90% by weight of solvent, with % by    weight based on the total weight of the one or more components,    preferably at least 95% by weight, preferably at least 99.5% by    weight.-   129. Process according to any one of the preceding statements,    wherein the mass flow rate of total quantity of solvent provided to    all reactors is at least 4 times to at most 30 times the mass of    lactic acid provided to all reactors, preferably at least 6 times to    at most 25 times, preferably at least 9 to at most 20 times.-   130. Process according to any one of the preceding statements,    wherein the one or more components provided to the at least one    reactor comprises at least 1% by weight of catalyst system and at    most 25% by weight of catalyst system, with % by weight based on the    total weight of the one or more components, preferably at least 3%    by weight and at most 10% by weight, with % by weight based on the    total weight of the one or more components provided to the at least    one reactor.-   131. In some embodiments, the one or more components provided to the    at least one reactor comprises at most 1.00% by weight of organic    acids other than lactic acid, preferably at most 0.10% by weight,    preferably at most 0.01% by weight, with % by weight based on the    total weight of the one or more components provided to the at least    one reactor.-   132. Process according to any one of the preceding statements,    wherein the step of recovering at least part of the thermal energy    is performed prior to the step of purifying the recovered lactide.-   133. Process according to any one of the preceding statements,    wherein the step of recovering at least part of the thermal energy    is performed prior to the purifying crystallization step.-   134. Process according to any one of the preceding statements,    wherein the step of recovering at least part of the thermal energy    is performed during the step of purifying the recovered lactide.-   135. Process according to any one of the preceding statements,    wherein the step of recovering at least part of the thermal energy    is performed during the purifying crystallization step.-   136. Process according to any one of the preceding statements,    wherein the step of purifying the recovered lactide comprises a    solvent-solvent extraction step.-   137. Process according to any one of the preceding statements,    wherein the step of purifying the recovered lactide comprises a    filtration step, preferably through a membrane.-   138. Process according to any one of the preceding statements,    having a lactide yield of at least 60%, preferably at least 65%,    preferably at least 70%, preferably at least 75%, preferably at    least 80%, preferably at least 85%.-   139. Process according to any one of the preceding statements,    further comprising the step of: converting at least part of the    recovered lactide into polylactic acid.

In what follows, the invention will be discussed in more detail.Explicitly exemplified and/or preferred embodiments of one aspectdiscussed below, should also be considered as explicitly exemplifiedand/or preferred embodiments for the other aspects discussed below.

The present invention relates to a process for synthesizing lactide,preferably an industrial process for synthesizing lactide. The processcomprises the steps of: providing one or more components to at least onereactor, the one or more components comprising lactic acid; convertingat least part of the lactic acid into lactide and water, preferably inone step; and recovering at least part of the lactide. Preferably, thestep of converting at least part of the lactic acid into lactide andwater is performed in one step.

In some embodiments, the one or more components comprise at least onesolvent. In some embodiments, the one or more components comprise atleast one catalyst system. In some embodiments, the one or morecomponents comprise at least one solvent and at least one catalystsystem.

In some embodiments, the process comprises the step of: recovering atleast part of the water, optionally wherein the recovered watercomprises at least part of the at least one catalyst system. In someembodiments, the process comprises the step of: recovering at least partof the at least one catalyst system, optionally wherein the recoveredcatalyst system is comprised in at least part of the water. In someembodiments, the process comprises the step of: recovering at least partof the water and at least part of the at least one catalyst system,wherein the recovered water comprises at least part of the at least onecatalyst system.

In some embodiments, the process comprises the step of: recovering atleast part of the at least one solvent.

In some embodiments, the process comprises the steps of converting atleast part of the lactic acid into lactide and water and into lacticacid oligomers, preferably in one step; and recovering at least part ofthe lactic acid oligomers.

In some embodiments, the process comprises the step of: adding thermalenergy to at least one of the one or more components. In someembodiments, the step of adding thermal energy to at least one of theone or more components is performed prior to the step of adding the oneor more components to the at least one reactor. In some embodiments, theprocess comprises the step of recovering thermal energy from at leastone of the one or more recovered components.

In some embodiments, the process comprises the step of providing the oneor more components to at least two reactors, preferably to at least tworeactors connected in series.

In some particularly preferred embodiments, the invention provides aprocess for synthesizing lactide, comprising the steps of adding thermalenergy to at least one solvent; providing one or more components to atleast one reactor, the one or more components comprising lactic acid andthe at least one solvent; converting at least part of the lactic acidinto lactide and water, preferably in one step; and recovering at leastpart of the lactide. The step of adding thermal energy to the at leastone solvent is performed prior to the step of adding the at least onesolvent to the at least one reactor.

Such a process has the advantage that heat is added to the solvent,which solvent is then used to (partially) heat the reactor(s). Theamount of solvent and the temperature of the solvent can be modified tosuit the lactic acid feed. This provides a more flexible process. Such aprocess also has the advantage that the reactor(s) requires less, oreven no, heating elements. This allows for a cheaper and simpler reactordesign. In addition, the heat exchanger on the feed and catalyst linecan be removed and add all of the required thermal energy to the solventflow. This reduces process CAPEX and improves the reliability regardingthe fact that feed stream contains solid catalyst and it is better toreduce the unit operations on this line.

Another advantage is that such a process is more productive compared toa process that requires heat elements in the reactor, for example heatexchanger tubes. The process that occurs in a reactor without heatingelements allows a better mixing because there are less or no obstaclesin the reactor. Obstacles in the reactor, such as heating elements,disturb the movement of fluid or slurry in the reactor, creating zonesin the reactor where the fluid is stationary or where the fluid ismoving more slowly than normally in the reactor. In these zones,reagents may not be fed fast enough into the zone, reaction product isbeing built up in said zone, solid catalyst—if present—precipitates,and/or heat is not transferred in the same way as in other places in thereactor. All these events have an effect on the kinetics and thethermodynamics of the reaction, resulting in negative effects on theyield and the productivity of the reaction.

When using heating elements, the temperature in the direct zone aroundthe heating element is often higher than the temperature in the rest ofthe reactor, and often higher than the optimal temperature for thereaction to occur. In this hot zone, side reactions can occur. Anelevated temperature also promotes the formation of lactic acidoligomers, which lowers the overall yield of the lactide formationreaction. Especially combined with the mixing deficiencies as describedbefore, the heating elements can cause zones where the heat is nottransferred properly, resulting in significant amounts of lactic acidoligomers.

Yet another advantage of such a process is that mixing requires lessenergy, because the preheated solvent causes a convective flow in thereactor.

Another advantage is noticeable when solids are present in the reactionmixture, for example an optional catalyst on a solid support. Saidsolids will collide with objects, such as heating elements, in thereactor. These collisions will erode the objects in the reactor,shortening their lifespan. When the solids are catalyst particles, theseparticles will also undergo damage from the collision with the objects,reducing the lifespan of the catalyst. Avoiding the need for suchobjects in the reactor takes away these disadvantages and prolongs thelifespan of an optional catalyst. Furthermore, this may also preventerosion of equipment that is placed in the reactor.

Use of two reactors in series may permit an increase of the overallprocess conversion, particularly in the case of adding an additionalintermediate water separation step between the two reactors.

Separate entry of solvent and feed may permit to use the solvent flowfor reactor heating and may avoid high heating of the feed. The heatexchanger on the feed entry may be totally eliminated. Instead, thesolvent may be heated to higher temperatures to compensate this impact.This may reduce process CAPEX and may decrease process liability as lessunit operations may be employed on the feed line which typicallycontains dispersed catalysts in slurry phase.

A solvent may be either injected only into the first reactor, or it maybe divided into separate entries for each reactor. In this case, eachreactor may be heated independently by adjusting the inlet flow rate ofsolvent in each reactor. This brings about the advantage of processflexibility in terms of temperature. In addition, the overall solventvolume in the first reactor may be less compared to the single entrycase. Therefore, the available reactor volume for the feed may increasewhile the reactor volume is fixed. Therefore, the residence time of thereactants may increase and the overall conversion may be improved.Preferably, the solvent quantity remains above a minimum requiredsolvent amount to dissolve all of the produced lactide.

In case of single entry for feed and solvent, a big slurry pump istypically used for whole fluids. By separating two fluids, a smallerslurry pump may be used for feed and catalyst inlet and anotherconventional pump may be used for the solvent inlet. In addition,regarding the fact that the feed line may have a lower pressure comparedto the solvent line, less compression may be required for the solventcompared to the single pump condition. This results in OPEX saving.

The at least one solvent is provided in the at least one reactorindependently from the lactic acid by a separate entry into the at leastone reactor. Such a process also has the advantage that the heatedsolvent is independently added to the reactor(s) from the lactic acidfeed. Such a process has the advantage that a smaller, slurry pump willbe used, instead of a larger slurry pump. This allows for a cheaper,simpler and more reliable pump design.

In some preferred embodiments, prior to the step of adding the at leastone solvent to the at least one reactor, the solvent has a temperatureof at least 140° C. and at most 300° C.; preferably of at least 150° C.and at most 250° C.; preferably of at least 160° C. and at most 210° C.The solvent may be used to heat up the reactor(s). The solvent may beused to heat up the other components provided to the reactor(s).

In some preferred embodiments, prior to the step of adding the at leastone solvent to the at least one reactor, the solvent has a temperatureof at least 5° C. greater than the temperature of the lactic acid,preferably of at least 10° C. greater than the temperature of the lacticacid, preferably of at least 20° C. greater than the temperature of thelactic acid, preferably of at least 30° C. greater than the temperatureof the lactic acid, preferably of at least 40° C. greater than thetemperature of the lactic acid, preferably of at least 50° C. greaterthan the temperature of the lactic acid, preferably of at least 60° C.greater than the temperature of the lactic acid, preferably of at least70° C. greater than the temperature of the lactic acid, preferably of atleast 80° C. greater than the temperature of the lactic acid. Thesolvent may be used to heat up the lactic acid.

In some preferred embodiments, prior to the step of adding the at leastone solvent to the at least one reactor, the solvent has a temperatureof at least 5° C. and at most 100° C. greater than the temperature ofthe lactic acid, preferably of at least 10° C. and at most 80° C.greater, and preferably of at least 15° C. and at most 50° C. greater.

In some preferred embodiments, the one or more components are providedto at least two reactors, preferably to at least two reactors connectedin series. Such processes have the advantage that one of the reactorsmay be by-passed in case of a malfunction. Moreover, the overallreaction conversion increases thanks to use of reactors in series.

In some preferred embodiments, the process comprises the step ofrecovering at least part of the water, wherein the at least part of thewater is recovered between the at least two reactors. Such processespermit water separation and increase the conversion in the secondreactor. Such processes also reduce the risk of lactide hydrolysis intolactic acid. In some preferred embodiments, at least 50% of the water isrecovered between the at least two reactors, based on the total amountof water exiting the first reactor of the at least two reactors,preferably by distillation, decantation, and/or filtration.

In some preferred embodiments, the at least one solvent is divided intoat least two solvent fractions, wherein each solvent fraction isseparately provided to each reactor of the at least two reactors. Insome preferred embodiments, the at least two solvent fractions comprisea first solvent fraction and a second solvent fraction, wherein at leastpart of the thermal energy is added to the first solvent fraction. Insome preferred embodiments, the at least two solvent fractions comprisea first solvent fraction and a second solvent fraction, wherein at leastpart of the thermal energy is added to the second solvent fraction. Suchprocesses allow for a better control of the amount of solvent added toeach reactor, and a better control of the amount of heat added to eachsolvent. This allows for an independent control of the reactor settingsof each reactor. It also reduces the solvent content in the firstreactor and hence increases the reactor volume available to thereactant. Therefore, the reactant residence time increases andconsequently reaction conversion will improve.

Preferably, more solvent is added to the first reactor and less solventis added to the second reactor. Such processes improve product yield andoverall conversion. Such processes also improve the residence time ofthe components in the first reactor for identical reactor volume. Suchprocesses also improve the overall conversion. In some preferredembodiments, the process comprises the steps of: providing a firstsolvent fraction comprising at least 50% and at most 100% of the atleast one solvent, preferably at least 60% and at most 85% of the atleast one solvent, to the first reactor of the at least two reactors;and providing a second solvent fraction comprising at least 0% and atmost 50% of the at least one solvent, preferably at least 15% and atmost 40% of the at least one solvent, to the second reactor of the atleast two reactors; with % based on the total sum weight of the firstsolvent fraction and the second solvent fraction. Typically, thepercentages add up to 100%. The amount of solvent added may depend onthe solubility of lactide in the solvent. It is preferably at most 20times the lactic acid content of feed, preferably at most 15 times,preferably at most 10 times, preferably at most 8 times, compared byweight.

In some preferred embodiments, the thermal energy added to the at leastone solvent is at least partly recovered thermal energy, preferablywherein the partly recovered thermal energy was recovered from recoveredsolvent and/or recovered water. This allows for energetic optimizationas also discussed elsewhere in the present description.

In some particularly preferred embodiments, the invention provides aprocess for synthesizing lactide comprising the steps of: providing oneor more components to at least one reactor, the one or more componentscomprising lactic acid; converting at least part of the lactic acid intolactide and water and into lactic acid oligomers, preferably in onestep; recovering at least part of the lactide; recovering at least partof the water and at least part of the lactic acid oligomers; adding afeed, optionally comprising lactic acid oligomers, and optionallycomprising water, to the recovered water and the recovered lactic acidoligomers, and mixing the feed with the recovered water and therecovered lactic acid oligomers to form a mixture; converting at leastpart of the lactic acid oligomers in the mixture into lactic acid andinto lactic acid dimer, preferably in one step; and removing at leastpart of the water from the mixture; whereby at least part of theremainder of the mixture is provided as one of the one or morecomponents that are provided to the at least one reactor. Lactic aciddimer may also be known as L2A, lactyl lactate, or lactoyl lactate,shown in formula (I).

The process may add the water that is obtained after the reaction to theoriginal lactic acid feed. Subsequently, a quantity of water ispreferably removed, to provide a fixed amount of water in the feed thatenters the reactor(s). Such a process has the advantage that the watercontent of the feed actually added to the reactor(s), is independent ofthe water content of the original feed, since the water quantity thatenters reactor is separately controlled. Typically, the original feedwill have a wide range of possible concentrations for lactic acid, whichmay range from 1% to 100% by weight of the total original feed,typically from 5% to 95%, typically from 15% to 90%. Such a processleads to an increased flexibility of the process, depending on theoriginal feed, for identical or similar production capacity. Such aprocess also has the advantage that no distillation for the separationlactic acid, and an optional catalyst, from water is required. Forexample, separation by membrane may be sufficient. Such a process alsohas the advantage that the water is typically under pressure, and theseparation is therefore efficient. In addition, water is hot in thiscase and this enhances the hydrolysis of the feed oligomers to lacticacid and lactic acid dimer to produce the reactants of Lactideproduction reaction. There is furthermore no need to add water from anexternal source. Furthermore, the high temperature of water isadvantageous for catalyst regeneration with this water.

Mixing the feed with a water line after a decantation step, permits toincrease the temperature of the feed and its water concentration to easethe hydrolysis of the oligomers. This ease in hydrolysis may avoid aseparate cracking step for the oligomers to convert them into startingmaterial. Hence a separation step may be avoided, no separate equipmentmay need to be foreseen for the cracking step, no reagents may need tobe supplied to the separate cracking step, and/or no energy may need tobe used for the separate cracking step. Mixing feed and the watercontaining line from a decantation step permits to recover the heatcontent of this stream by heating. Therefore, feed may be heated withoutuse of an additional heat exchanger. In addition, the temperature of theflow into the water separation step may be reduced. This may results ineasier water separation and less heat loss via separated water. Theprocess allows using a single water separation step, and preferably onesingle water separator, to at least partially dewater the feed and to atleast partially dewater the recovered water that comprises at least partof the lactic acid oligomers.

In some preferred embodiments, the one or more components provided tothe at least one reactor comprises at least 1% by weight of lactic acidand at most 100% by weight of lactic acid, with % by weight based on thetotal weight of the one or more components, preferably at least 5% byweight and at most 95% by weight, preferably at least 15% by weight andat most 90% by weight. Because the quantity of water is controlled priorto entering the reactor(s), the quantity of lactic acid in the originalfeed may fluctuate.

In some preferred embodiments, the step of converting at least part ofthe lactic acid oligomers in the mixture into lactic acid and intolactic acid dimer is performed through hydrolysis by the recovered waterand/or through hydrolysis by water present in the feed. During thereaction, oligomers be formed, herein referred to as L3A. L4A, etc. Sucholigomers are typically not converted to lactide, in the presence oflactic acid. Such oligomers may also clog the pores of a zeolitecatalyst. Using the water as a carrier solvent, accumulated oligomerscould be removed. In addition, with the same water, they may behydrolyzed back to lactic acid, herein referred to as LA, or to thedimer of lactic acid, herein referred to as L2A. By using such aregeneration strategy, all carbon coming from the reaction compounds canbe reintroduced into the system, without any losses. The inventors havefound that relatively short reaction times may be required to remove andconvert all carbon originating from the feedstock: oligomers weretypically removed after 15 min of extraction. This allows for efficientprocess, without the need of separating the oligomers and hydrolyzingthe oligomers separately or forming lactide from the oligomersseparately. The oligomers may be hydrolyzed back to LA and L2Aon-the-fly.

In some preferred embodiments, the one or more components comprise atleast one catalyst system, and wherein the process comprises the stepsof: providing at least one catalyst system to the at least one reactor;recovering at least part of the at least one catalyst system; andregenerating at least part of the recovered catalyst system.

In some preferred embodiments, the step of regenerating at least part ofthe recovered catalyst system is performed through hydrolysis by therecovered water and/or through hydrolysis by water present in the feed.For example, when a zeolite catalyst is used, the zeolite may beregenerated by the water. The zeolite typically retrieves its initialactivity after such processes. Such processes have the advantage thatthe water is typically hot (and possibly under pressure), and thereaction is therefore efficient. There is furthermore no need to addwater from an external source.

In some preferred embodiments, the at least one catalyst system isregenerated in-line with the at least one reactor. This allows forefficient process, without the need of separating the catalyst andregenerating the catalyst separately. The catalyst may be regeneratedon-the-fly. Such processes have the advantage that the catalyst cycle isclosed. It is therefore possible to work without external catalystsource, or even without a catalyst. In some preferred embodiments, theat least one catalyst system comprises an acidic zeolite, preferablyH-BEA. Acidic zeolites, and H-BEA in particular, are well-suited forregeneration through hydrolysis, particularly with the present water atelevated temperatures.

In some preferred embodiments, the step of removing at least part of thewater from the mixture is performed with a membrane.

In some preferred embodiments, the feed comprises lactic acid oligomers(LxA, wherein x is equal to or greater than 3). Such processes have theadvantage that the lactic acid oligomers in the feed are converted intolactic acid and lactic acid dimer by the water at elevated temperature,prior to being fed to the reactor. Furthermore, the zeolite catalyst mayalso catalyze the hydrolysis of oligomers in the zeolite itself,providing autocatalyzed regeneration. In some preferred embodiments, thefeed comprises at most 50% by weight lactic acid oligomers; preferablymost 15% by weight lactic acid oligomers; preferably about 10% by weightlactic acid oligomers; with % by weight compared to the total weight oflactic acid, lactic acid dimer, and lactic acid oligomers combined.Concentration of oligomers can rise up to 55% (including L2, L3, Lx . .. ) in case of a solution with initial 100% LA. The optimum case iswhere 30% is water, 60% LA, 9% L2A, and 1.0% LxA.

In some preferred embodiments, the step of converting at least part ofthe lactic acid oligomers in the mixture into lactic acid and intolactic acid dimer, and optionally the step of regenerating at least partof the recovered catalyst system, is performed in one or more recyclingpipes. Such processes have the advantage that no separate regenerationreactor is required. Additional heating may be provided to the recyclingpipes.

Mixing the feed with the water line after the decantation step permitsto increase the temperature of the feed and its water concentration toease the hydrolysis of the oligomers. Mixing feed and the watercontaining line from the decantation step permits to recover the heatcontent of this stream by heating. Therefore, feed is heated without useof an additional heat exchanger. In addition, the temperature of theflow into the water separation step will be reduced. This may result ineasier water separation and less heat loss via separated water.

In some particularly preferred embodiments, the invention provides aprocess for synthesizing lactide, comprising the steps of: addingthermal energy to at least one of one or more components; providing theone or more components to at least one reactor, the one or morecomponents comprising lactic acid; converting at least part of thelactic acid into lactide and water, preferably in one step; recoveringat least part of the lactide; recovering at least part of the thermalenergy; and adding the recovered thermal energy to at least one of theone or more components. Such a process has the advantage that it is nottoo energy consuming.

The term “one step reaction” refers to a reaction wherein reagents aretransformed in the desired reaction products by passing through one ormore transition states, without the formation of intermediates that arebe isolated and separated from the rest of the reaction mixture.Typically, a one step reaction is performed in one reactor with a singleset of reaction conditions.

The term “two step reaction” refers to a reaction wherein reagents aretransformed in the desired reaction products by passing through at leastone first transition state to form an intermediate, followed by passingthrough at least one second transition state, before yielding thedesired product. Different reaction conditions can be used to reach theat least first transition state than the reaction condition to reach theat least one second transition state. Said intermediate can be isolatedand separated from the rest of the reaction mixture. Typically, a twostep reaction is performed in two or more (sequential) reactors, eachwith an independent set of reaction conditions.

In some preferred embodiments, the process comprises the step of:recovering at least part of the water, wherein at least part of therecovered thermal energy is recovered from the recovered water.

In some preferred embodiments, the one or more components comprise atleast one solvent, and the process comprises the step of: recovering atleast part of the at least one solvent; wherein at least part of therecovered thermal energy is recovered from the recovered solvent.

Direct heat recovery from the solvent may be limited to a minimumtemperature in range of 80° C. to 130° C. depending on the solventnature and solubility of for example decane in the solvent. Cooling thesolvent below this temperature limit may result in crystallization ofthe lactide inside the heat exchangers. Preferably, the heat from thecrystallization step is recovered to heat the inlet fluids into thereactor. Crystallization may be carried out in more than one step toease heat recovery.

The energy in the water containing line separated in the decantationstep may be recovered to minimize the heat loss via the water outletfrom the water separation unit. This energy may be recovered by heatingthe feed thanks to mixing the feed and the water containing line fromdecantation. This energy recovery may be done by use of a heat exchangeron this line as well. In this case CAPEX may increase as an additionalheat exchanger is required.

In some preferred embodiments, at least part of the recovered thermalenergy is recovered from the recovered lactide. In some preferredembodiments, the step of recovering at least part of the lactidecomprises a first crystallization step and a second crystallizationstep. In some preferred embodiments, the first crystallization step andthe second crystallization step are each independently cooled. In somepreferred embodiments, the step of recovering at least part of thethermal energy is performed during the first crystallization step. Insome preferred embodiments, the step of recovering at least part of thethermal energy is performed during the second crystallization step. Suchprocesses have the advantage that the heat extraction necessary forcrystallizing the lactide is used to heat up components that areprovided to the reactor(s). In some preferred embodiments, at least partof the recovered thermal energy is added to the lactic acid. In somepreferred embodiments, the one or more components comprise at least onesolvent, and at least part of the recovered thermal energy is added tothe solvent.

In some preferred embodiments, at least part of the recovered thermalenergy is recovered from the recovered water, and at least part of therecovered thermal energy is added to the lactic acid. This is preferablyperformed by direct mixing of the feed and the separated water fromdecantation. Therefore no heat exchanger is required, which reducesCAPEX.

In some preferred embodiments, at least part of the recovered thermalenergy is recovered from the recovered water, and at least part of therecovered thermal energy is added to the solvent. In some preferredembodiments, at least part of the recovered thermal energy is recoveredfrom the recovered solvent and at least part of the recovered thermalenergy is added to the lactic acid. In some preferred embodiments, atleast part of the recovered thermal energy is recovered from therecovered solvent, and at least part of the recovered thermal energy isadded to the solvent. In some preferred embodiments, at least part ofthe recovered thermal energy is recovered from the recovered lactide,and at least part of the recovered thermal energy is added to the lacticacid. In some preferred embodiments, at least part of the recoveredthermal energy is recovered from the recovered lactide, and at leastpart of the recovered thermal energy is added to the solvent.

In some preferred embodiments, at least part of the recovered thermalenergy is recovered from the recovered water, at least part of therecovered thermal energy is recovered from the recovered solvent, atleast part of the recovered thermal energy is recovered from therecovered lactide, and at least part of the recovered thermal energy isadded to the solvent. Heat recovery to the solvent provides a heatedsolvent. Advantages of a heated solvent are described above.

Such processes, individually and/or combined, have the advantage thatthe individual processes are energetically optimized, and/or that theoverall process is energetically optimized.

Preferably, at least 40% of the thermal energy is recovered from theflows leaving the reactor, preferably at least 50%, preferably at least60%, preferably at least 70%. Heat exchangers may be used. The type ofheat exchanger may differ, but is preferably selected from the groupcomprising tube and shell heat exchanger, plate heat exchanger, plateand shell heat exchanger, adiabatic wheel heat exchanger, plate fin heatexchanger, fluid heat exchangers, waste heat recovery units, dynamicscraped surface heat exchanger, phase-change heat exchangers, directcontact heat exchangers or microchannel heat exchangers; more preferablya counter current heat exchanger; most preferably a tube and shellcounter current heat exchanger or a plate heat exchanger.

In some particularly preferred embodiments, the invention provides aprocess for synthesizing lactide, comprising the steps of: providing oneor more components to at least one reactor, the one or more componentscomprising lactic acid; converting at least part of the lactic acid intolactide and water, preferably in one step; recovering at least part ofthe lactide; and recovering at least part of the water, wherein the stepof recovering at least part of the water comprises a decantation step,with the proviso that the step of recovering at least part of the waterdoes not comprise an azeotropic distillation step.

Such a process has the advantage that a multi-step recovery of water maynot be required. Such a process has the advantage that no heating isneeded. Such a process has the advantage that it does not degrade thelactide thermally. Such a process has the advantage that it does notdegrade the solvent, which may be reused. Decantation of the separatedcatalyst in addition to the water separation may be performed thanks tothe usually hydrophilic nature of catalyst in addition catalystregeneration may start in this section thanks to high temperature andthe fact that the catalyst will be in a water phase.

Preferably, both water and catalyst are separated from the solventstream. Integrated water and catalyst separation may reduce the energyconsumption and process costs. Oligomers and unreached reactants may beseparated from the solvent to a large extent by the water stream.

The contact between the water and separated catalyst inside the decanterpermits to hydrolyze the oligomers inside the catalyst and to startcatalyst regeneration inside a decanter. This is especially interestingregarding the high water temperature in this unit which enhancesoligomer hydrolysis.

In some preferred embodiments, the one or more components comprise atleast one catalyst system and process comprises the step of: recoveringat least part of the water, wherein the recovered water comprises atleast part of at least one catalyst system. In some preferredembodiments, the at least one catalyst system comprises at least oneacidic zeolite, preferably H-BEA. Preferred zeolites are as describedfurther below. The decantation step is particularly efficient with ahydrophilic catalyst such as a zeolite.

As an alternative to decantation, a distillation option may be provideddirectly into the reactor for in situ water separation. Various kinds ofreactive distillation reactors may be used in this case. FIG. 3 showssome possible configurations. Depending on the nature of the solvent,other kind of designs may be used. Some advanced distillation systemssuch as divided wall column may be used to produce a concentratedlactide outlet stream inside the reactor to ease the downstreamseparation steps. The energy consumption may be reduced by use of heatintegration, to recover the evaporation energy which is inherent to thedistillation.

In some preferred embodiments, the process comprises the step of:providing one or more components to at least two reactors, preferably toat least two reactors connected in series. In some preferredembodiments, the at least part of the water is recovered between the atleast two reactors.

In some preferred embodiments, the step of recovering at least part ofthe lactide is performed by crystallization, preferably wherein the stepof recovering at least part of the lactide comprises a firstcrystallization step and a second crystallization step. The secondcrystallizer may be cooled partially or completely with cold waterdepending on the availability of cooling water.

In some embodiments, the crystallizer design results in formation ofsolids in form of solid crystals with a specific adjustable particlesize (the technology used for sugar grain production). This design mayrequire a solid separation step, which could be filtration orcentrifugal separation, among others. In some embodiments, thefiltration technology will be relatively challenging regarding the factthat the separated particles may need to be continuously separated andrecovered. This may be solved by an automated filtration system orcentrifugal separation. Centrifugal separation has the advantage ofoperating in continuous mode. The difficulty would be agglomeration ofLD particles and formation of a cohesive cake. This can be resolved bycontrolling the outlet pressure and temperature of the centrifugationunit to fluidize the separated solid LD on the walls of the unit.

In some preferred embodiments the process is performed with the provisothat the step of recovering at least part of the water does not comprisea liquid/liquid extraction step.

In some embodiments, the process comprises the step of: purifying therecovered lactide. The step of purifying the recovered lactide isperformed after the step of recovering the lactide. In some embodiments,the step of purifying the recovered lactide comprises a combination ofvacuum and heating. In some embodiments, the step of purifying therecovered lactide is performed at a pressure of at most 200 mbar, forexample of at most 100 mbar, for example of at least 20 mbar and at most40 mbar, preferably of about 30 mbar. In some embodiments, the step ofpurifying the recovered lactide is performed at a temperature of at mostthe melting point of lactide, preferably of at most 90° C., for exampleof at least 25° C. and at most 90° C. Such processes have the advantagethat less solvent is lost. Such processes also have the advantage thatthey provide energetic optimization. Such processes have the advantagethat no solvent flaring may be required. Preferably, purificationhappens after separation of Lactide by filtration from decane. Theseparate Lactide cake contains some solvent which should be separated toproduce high purity Lactide. In an alternative case, crystallization canbe carried out in an static crystallizer which separates the Lactide atthe end without a filtration step.

In some embodiments, the step of purifying the recovered lactidecomprises a purifying crystallization step. Lactide separation andpurification may also be carried out in a single static or dynamiccrystallizer without filtration. Preferably, the final lactide purity isat least 98.0%, preferably at least 99.0%, preferably at least 99.5%,preferably at least 99.9%.

In some preferred embodiments, the one or more components comprise asolvent that is non-miscible with water, preferably wherein the solventis isobutylbenzene. Such processes have the advantage of easiersolvent—water separation.

Preferably, the step of converting at least part of the lactic acid intolactide and water is performed in one step. The one step process forconverting lactic acid into lactide differs from the two-step synthesisin the art, in that water removal takes place during the ring-closingreaction and lactide is thus synthesized directly from aqueous lacticacid via condensation, rather than via transesterification. In somepreferred embodiments, the step of converting at least part of thelactic acid into lactide and water comprises a ring-closing reaction.Preferably the conversion of lactic acid into lactide is performed in asingle reactor. When multiple reactors are used, for example at leasttwo reactors connected in series, each reactor individually performs theone step conversion of lactic acid into lactide.

The one step conversion of lactic acid into lactide has the advantagethat less side products are formed, for example LxA oligomers, such asL3A and L4A oligomers. As used herein, the term “LxA” refers to oligomercomprising x basic lactic acid units. In general, the term LxA may beused to describe the ensemble of all oligomers, wherein x is equal to orgreater than 3. LxA oligomers are typically undesired in the presentprocesses, since they are not directly converted into lactide. The onestep conversion of lactic acid into lactide also has the advantage thatthere is less hydrolysis of lactide back into lactic acid.

Preferably, the process is an industrial process for synthesizinglactide. Preferably, the process has an output of at least 10 000 tonlactide per year, preferably at least 30 000 ton lactide per year,preferably at least 40 000 ton lactide per year, preferably at least 50000 ton lactide per year, preferably at least 60 000 ton lactide peryear, preferably at least 70 000 ton lactide per year, preferably atleast 80 000 ton lactide per year.

The reactor(s) may operate in a temperature of at least 120° C.,preferably at least 130° C., preferably at least 140° C., preferably atleast 150° C., preferably at least 160° C., preferably at least 170° C.

In some embodiments, the at least one reactor is a mixed reactor,preferably wherein the at least one reactor is mixed mechanically and/orwith internal or external fluid flow. In some preferred embodiments, theat least two reactors are mixed reactors, preferably wherein the atleast two reactors are mixed mechanically and/or with internal orexternal fluid flow.

In some embodiments, the step of adding thermal energy to at least oneof the one or more components is performed after the step of adding theat least one of the one or more components to the at least one reactor,for example by an internal exchanger or a jacketed wall. In someembodiments, the step of adding thermal energy to at least one of theone or more components is performed after the step of adding the atleast one of the one or more components to the at least two reactors,for example by an internal exchanger or a jacketed wall. Internal heatexchangers may be used. The reactor may be heated by heating up thesolvent entering into the reactor. A heat exchanger may be installedbetween two reactors.

In some embodiments, the step of recovering thermal energy is performedafter the last reactor of the at least one reactor or after the lastreactor of the at least two reactors. In some embodiments, the step ofrecovering thermal energy is performed between reactors of the at leastone reactor or after the last reactor of the at least two reactors. Insome embodiments, the step of recovering thermal energy is performedwith a heat exchanger. Heat exchangers are preferably used to transferthe heat from the hot outlet streams to the cool inlet flows beforeentering into the reactor.

In some embodiments, the lactic acid is converted into lactide in asingle reactor. In some embodiments, the lactic acid is independentlyconverted into lactide in each reactor of the at least two reactors.

In some embodiments, the one or more components comprise at least onesolvent. Use of a solvent may have the advantage that the lactide willbe dissolved in the solvent, thereby reducing lactide hydrolysis backinto lactic acid by the water. For example, in aromatic solvents, thelactide will prefer the organic phase. In some embodiments, the processcomprises the step of recovering the at least one solvent, preferablythe process comprises the step of recycling the at least one solvent.

An appropriate solvent may be one in which the reaction productsdescribed herein are soluble and which has an appropriate boiling point.More particularly, the boiling point preferably is sufficiently high sothat at the boiling point temperature an acceptable reaction rate isachieved, but sufficiently low such that the formation of degradationproducts can be avoided or minimized. In some embodiments, the solventforms a non-azeotropic mixture with water, thereby allowing the removalof water via distillation. Non-azeotropic solvents can include waterimmiscible aromatic solvents, water immiscible aliphatic or cyclichydrocarbon solvents, water soluble solvents, or mixtures thereof. Waterimmiscible non-azeotropic solvents are preferred because, afterdistillation, they can be readily separated with the solvent beingrecycled and the water being taken out of the system. Moreover,potential byproducts obtained during the reaction process (such as watersoluble short oligomers of the hydroxycarboxylic acid and/oraminocarboxylic acid) will typically dissolve in the water phase, whilethe cyclic esters and/or cyclic amides of interest typically remain inthe organic solvent phase. This may facilitate the separation of thebyproducts from the products of interest via extraction, and subsequentre-entry of the water soluble products (after hydrolysis) in thereaction process.

Solvents which are not preferred because of being potentially reactivewith cyclic esters include alcohols, organic acids, esters and etherscontaining alcohol, peroxide and/or acid impurities, ketones andaldehydes with a stable enol form, and amines.

Suitable solvents may include aromatic hydrocarbon solvents such asbenzene, toluene, xylene, ethylbenzene, trimethylbenzene (e.g.1,3,5-trimethylbenzene), methylethylbenzene, n-propylbenzene,isopropylbenzene, diethylbenzene, isobutylbenzene, triethylbenzene,diisopropylbenzene, n-amylnaphthalene, and trimethylbenzene; ethersolvents such as ethyl ether, isopropyl ether, n-butyl ether, n-hexylether, 2-ethylhexyl ether, ethylene oxide, 1,2-propylene oxide,dioxolane, 4-methyldioxolane, 1,4-dioxane, dimethyldioxane, ethyleneglycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycoldiethyl ether, diethylene glycol di-n-butyl ether, tetrahydrofuran, and2-methyltetrahydrofuran; aliphatic hydrocarbon solvents such asn-pentane, isopentane, n-hexane, isohexane, n-heptane, isoheptane,2,2,4-trimethylpentane, n-octane, isooctane, cyclohexane, andmethylcyclohexane; and ketone solvents such as acetone, methyl ethylketone, methyl n-propyl ketone, methyl n-butyl ketone, diethyl ketone,methyl isobutyl ketone, methyl n-pentyl ketone, ethyl n-butyl ketone,methyl n-hexyl ketone, diisobutyl ketone, trimethylnonanone,cyclohexanone, 2-hexanone, methylcyclohexanone, 2,4-pentanedione,acetonylacetone, acetophenone, and fenchone.

In some embodiments, the at least one solvent is a C₅-C₂₄ alkane or amixture of C₅-C₂₄ alkanes. In some embodiments, the at least one solventis decane. Alkanes, and decane in particular, have the advantage thatthey can easily be separated from water, for example in a phase settler.Furthermore, they have a relatively high boiling point. Furthermore,they pose less HSE risk. Furthermore, they are stable in boiling pointoperating conditions. Furthermore, they are relatively cheap.

In some embodiments, the at least one solvent is benzene, preferablysubstituted with one or more linear or branched C₁-C₄ alkyl groups, or amixture thereof. For example, the at least one solvent may be selectedfrom the group comprising: isobutylbenzene, toluene, ortho-xylene,meta-xylene, para-xylene, ethylbenzene, propylbenzene, trimethylbenzene,and mixtures thereof. In some embodiments, the at least one solvent isisobutylbenzene, cumene, o-xylene or toluene, preferablyisobutylbenzene. Substituted benzenes, and isobutylbenzene inparticular, have the advantage that they for a better emulsion withwater, and less agitation is required in the reactor(s). Furthermore,they have a relatively high boiling point. Furthermore, they provide ahigh yield of lactide. Furthermore, they provide a high solubility forlactide.

In some embodiments, the solvent has a standard boiling point of atleast 50° C. to at most 250° C., preferably of at least 100° C. to atmost 200° C., more preferably of at least 160° C. to at most 180° C.isobutylbenzene and decane have a boiling point of about 175° C. PatentPending™

In some embodiments, the at least one catalyst system is dispersed inthe at least one reactor in form of a slurry. In some embodiments, oneor more of the one or more reactors comprise a separate catalyst entry,for example wherein the separate entry comprises of at least 50 wt %catalyst, preferably 70 wt % catalyst, preferably 80 wt % catalyst.

The inlet stream of the water separation unit typically contains a largecontent of catalysts (up to 30 wt %). This high catalyst content may beharmful for the membrane or filters used in the water separationsection. In some embodiments, a catalyst separation unit may beinstalled upstream of this unit to protect filters/membranes. In thiscase a hydro-cyclone or a centrifugal separator may be used to separatecatalyst and re-inject it into the reactor inlet stream or probablyre-inject directly into the reactor. Direct catalyst injection into thereactor has the advantage of being able to use normal pumps on thereactor inlet stream. Preferably, a semi-batch catalyst injectionsystems similar to the configuration proposed in FIG. 2 is used. Two orthree catalyst injection system can be installed for each reactordepending on the process configuration.

In some embodiments, the process comprises the step of recovering the atleast one catalyst system, preferably recycling the at least onecatalyst system. In some embodiments, the at least one catalyst systemis regenerated by the solvent. In some preferred embodiments, the atleast one catalyst system is regenerated by water. In some preferredembodiments, the at least one catalyst system is regenerated throughcalcination.

Preferably, the catalyst system comprises a zeolite catalyst. Zeolitecatalysts described herein may be regenerated and reused in the process.Accordingly, particular embodiments of the process described herein maycomprise a step of regenerating the zeolite catalyst. Regeneration ofthe zeolite catalysts can be performed via washing or calcination.Preferably, regeneration of the zeolite catalysts is done viacalcination, for example at a temperature of at least 150° C. Inparticular embodiments, the calcination temperature is at least 200° C.,for example at least 300° C., for example at least 400° C., for exampleabout 450° C. In some embodiments, the at least one catalyst systemcomprises at least one acidic zeolite. The term “zeolite” as used hereinrefers to both natural and synthetic microporous crystallinealuminosilicate materials having a definite crystalline structure asdetermined by X-ray diffraction. A zeolite comprises a system ofchannels which may be interconnected with other channel systems orcavities such as side-pockets or cages. The channel systems may bethree-dimensional, two-dimensional or one-dimensional. A zeolitecomprises SiO₄ and XO₄ tetrahedra, wherein X is Al (aluminium) or B(boron). A zeolite may comprise a combination of AlO₄ and BO₄tetrahedra. In a preferred embodiment, X is Al. and the zeolitecomprises no BO₄ tetrahedra. The SiO₄ and XO4 tetrahedra are linked attheir corners via a common oxygen atom. The Atlas of Zeolite FrameworkTypes (C Baerlocher, L B McCusker, D H Olson, 6th ed. Elsevier,Amsterdam, 2007) in conjunction with the web-based version(http://www.iza-structure.org/databases/”) is a compendium oftopological and structural details about zeolite frameworks, includingthe types of ring structures present in the zeolite and the dimensionsof the channels defined by each ring type. Proven recipes and goodlaboratory practice for the synthesis of zeolites can be found in the“Verified synthesis of zeolitic materials” 2nd Edition 2001. Variousproven recipes for the synthesis comprising BO₄ tetrahedra areavailable. For example, the synthesis and characterization ofboron-based zeolites having a MFI topology has been described byCichocki and Parasiewicz-Kaczmarska (Zeolites 1990, 10, 577-582).

In some embodiments, the at least one catalyst system comprises at leastone acidic zeolite comprising: two or three interconnected andnon-parallel channel systems, wherein at least one of said channelsystems comprises 10- or more-membered ring channels; and a frameworkSi/X₂ ratio of at least 24 as measured by NMR; or three interconnectedand non-parallel channel systems, wherein at least two of said channelsystems comprise 10- or more-membered ring channels; and a frameworkSi/X₂ ratio of at least 6 as measured by NMR; wherein each X is Al or B.

As used herein, the term “channel system” refers to a system of paralleland crystallographically equivalent channels, wherein the channels are8-membered ring channels or larger, for example wherein the channels are10-membered ring channels or 12-membered ring channels. Accordingly, asused herein, the term “channel” refers to an 8- or more membered ringchannel which is part of a system of parallel and crystallographicallyequivalent channels.

Preferred zeolites for use in the present process comprise 10- ormore-membered ring channels, such as 10-membered ring channels (10MR),12-membered ring channels (12MR), or larger. The ring size for eachknown zeolite framework type is provided in the Atlas of ZeoliteFramework Types (C Baerlocher, L B McCusker, D H Olson, 6th ed.Elsevier, Amsterdam, 2007), which is incorporated herein by reference.

As used herein the terms “8-membered ring channels” or “8MR” refer to achannel comprising unobstructed 8-membered rings, wherein the 8-memberedrings define the smallest diameter of the channel. An 8-membered ringcomprises 8 T atoms, and 8 alternating oxygen atoms (forming the ring),wherein each T is Si, Al or B. As used herein the terms “10-memberedring channels” or “10MR” refers to a channel comprising unobstructed10-membered rings, wherein the 10-membered rings define the smallestdiameter of the channel. A 10-membered ring comprises 10 T atoms, and 10alternating oxygen atoms (forming the ring), wherein each T is Si, Al orB. As used herein the terms “12-membered ring channels” or “12MR” refersto a channel comprising unobstructed 12-membered rings, wherein the12-membered rings define the smallest diameter of the channel. A12-membered ring comprises 12 T atoms, and 12 alternating oxygen atoms(forming the ring), wherein each T is Si, Al or B. As used herein, theterm “10-or-more-membered ring channel” refers to a 10-membered ringchannel or larger, and therefore comprises for example both 10-memberedring channels and 12-membered ring channels.

The framework Si/X₂ ratio may be determined via Nuclear MagneticResonance (NMR) measurements, more particularly 29Si and 27Al NMR. Insome embodiments, X is Al. In a preferred embodiment, there is noframework B, and the Si/X₂ ratio is equal to the Si/Al₂ ratio. Thedetermination of the Si/Al₂ ratio by NMR may be performed as describedby Klinowski (Ann. Rev. Mater. Sci. 1988, 18, 189-218); or as describedby G. Engelhardt and D. Michel (High-Resolution Solid-State NMR ofSilicates and Zeolites. John Wiley & Sons, Chichester 1987. xiv, 485pp). The determination of the Si/B₂ ratio by NMR may be performed asdiscussed by D. Trong On et al. (Studies in Surface Science andCatalysis 1995, 97, 535-541; Journal of Catalysis, November 1995, Volume157, Issue 1, Pages 235-243).

The preferred zeolites used in the process described herein may compriseAlO₄ tetrahedra, BO₄ tetrahedra, or both. Accordingly, in someembodiments, X₂ is (Al₂+B₂). Thus, for a given zeolite, the Si/X₂framework ratio remains the same upon substitution of framework Al by B,or vice versa. However, it is envisaged that in particular embodiments,the zeolites may not comprise BO₄ tetrahedra, or an insignificant amountthereof (e.g. an A/B ratio of 100 or more). Thus, in particularembodiments, X₂ may be Al₂. The Si/X₂ ratios referred to herein aremolar ratios as determined via NMR, unless specified otherwise. It willbe understood by the skilled person that the Si/X2 ratio referred toherein is equal to the SiO₁/X₂O₃ molar ratio, wherein X₂O₃ is (Al₂O₃and/or B₂O₃). Moreover, the skilled person will understand that bydividing the Si/X₂ ratio by two, the Si/X molar ratio is obtained,wherein X is (Al and/or B). Accordingly, in some embodiments, thezeolite(s) for use in the process described herein may comprise aframework Si/X₂ ratio of at least 24, for example a framework Si/Al₂ratio of at least 24, wherein the zeolite further comprises at least twointerconnected and non-parallel channel systems wherein at least one ofthe interconnected and non-parallel channel systems comprises 10- ormore-membered ring channels, i.e. at least one of the channel systemscomprises 10- or more-membered ring channels, and at least one otherchannel system comprises 8- or more-membered ring channels. Examples ofsuch zeolites are zeolites comprising a topology selected from the groupcomprising FER, MFI, and MWW.

In some embodiments, both of the at least two channel systems comprise10- or more-membered ring channels. In some embodiments, at least one ofthe channel systems comprises 12- or more-membered ring channels.

In some embodiments, the zeolite for use in the process described hereinmay comprise a framework Si/X₂ ratio of at least 6, for example aframework Si/Al₂ ratio of at least 6; wherein the zeolite furthercomprises three interconnected and non-parallel channel systems whereinat least two of the interconnected and non-parallel channel systemscomprise 10- or more-membered ring channels, i.e. at least two of thechannel systems comprise 10- or more-membered ring channels, and theother channel system comprises 8- or more-membered ring channels.Examples of such zeolites include, but are not limited to zeolitescomprising a topology selected from the group comprising BEA, FAU, andMEL.

In some embodiments, the three channel systems all comprise 10- ormore-membered ring channels. In particular embodiments, at least one ofthe channel systems comprises 12- or more-membered channels. In someembodiments, at least two of the channel systems comprise 12- ormore-membered ring channels. Examples of such zeolites include, but arenot limited to zeolites comprising a topology selected from the groupcomprising BEA and FAU.

Preferably, the channels defined by the zeolite topology are largeenough to be accessible for the lactic acid monomers, but small enoughto prevent significant formation and/or diffusion of trimers or higherorder oligomers. Accordingly, in some embodiments, the zeolite onlycomprises channels with a ring size of at most 18, preferably of at most14, for example of at most 12.

In some embodiments, the zeolite for use in the process described hereincomprises a topology selected from the group comprising: BEA, MFI, FAU,MEL, FER, and MWW. These zeolites provide a particularly highselectivity towards lactide. In certain embodiments, the zeolite(s)comprise a topology selected from the group consisting of BEA, MFI, FAU,and MWW. In specific embodiments, the zeolite(s) comprise a zeolite witha BEA topology. In some embodiments, the acidic zeolite comprises atopology selected from the group comprising BEA, MFI, FAU, MEL, FER, andMWW, preferably BEA. In some embodiments, the at least one catalystsystem comprises an acidic zeolite, preferably wherein the at least onecatalyst system comprises an H-BEA zeolite. Exemplary commerciallyavailable zeolites suitable for use in the processes described hereininclude, but are not limited to, Beta polymorph A (BEA topology), ZSM-5(Mobil; MFI topology), Y zeolite (FAU topology), and MCM-22 (Mobil; MWWtopology).

In some embodiments, the zeolite comprises channels having an average(equivalent) diameter of at least 4.5 Å. More particularly, the zeolitemay comprise two or more non-parallel channels having an averagediameter of at least 4.5 Å. The channel diameter may be determinedtheoretically via knowledge of the zeolite framework type, or via x-raydiffraction (XRD) measurements, as will be known by the skilled person.Preferably, the zeolite comprises two or more non-parallel andinterconnected channels having an average (equivalent) diameter between4.5 and 13.0 Å, more preferably between 4.5 and 8.5 Å. Preferably, thediameter for the appropriate topology is obtained from internationalstandard literature: the Atlas of Zeolite structures or thecorresponding online database, found athttp://www.iza-structure.org/databases/, as referenced above. The(equivalent) diameter of the channels may also be determinedexperimentally via N2 adsorption, for example as discussed by Groen etal. (Microporous and Mesoporous Materials 2003, 60, 1-17), Storck et al.(Applied Catalysis A: General 1998, 174, 137-146) and Rouquerol et al.(Rouquerol F, Rouquerol J and Sing K, Adsorption by powders and poroussolids: principles, methodology and applications, Academic Press,London, 1999).

In some embodiments, the zeolite may further comprise mesopores. Thepresence of mesopores may increase the accessibility of the lactic acidto the micropores, and may therefore further increase the reactionspeed. However, it is also envisaged that the zeolite may not comprisemesopores. As used herein the term “mesopores” refers to pores in thezeolite crystal having average diameters of 2.0 nm to 50 nm. For poreshapes deviating from the cylinder, the above ranges of diameter ofmesopores refer to equivalent cylindrical pores. The mesopore averagediameter may be determined by gas sorption techniques such as N₂adsorption.

The zeolite(s) may be used as such, for example as a powder. In certainembodiments, the zeolite(s) may be formulated into a catalyst bycombining with other materials that provide additional hardness orcatalytic activity to the finished catalyst product. Materials which canbe blended with the zeolite may be various inert or catalytically activematerials, or various binder materials. These materials includecompositions such as kaolin and other clays, phosphates, alumina oralumina sol, titania, metal oxide such as zirconia, quartz, silica orsilica sol, metal silicates, and mixtures thereof. These components areeffective in densifying the catalyst and increasing the strength of theformulated catalyst. Various forms of rare earth metals can also beadded to the catalyst formulation. The catalyst may be formulated intopellets, spheres, extruded into other shapes, or formed into spray-driedparticles. The amount of zeolite which is contained in the finalcatalyst product may range from 0.5 to 99.9 weight %, preferably from2.5 to 99.5 weight % of the total catalyst, preferably from 2.5 to 95weight %, preferably from 2.5 to 90 weight % of the total catalyst, mostpreferably from 2.5 to 80 weight %; for example from 20 to 95 weight %,preferably from 20 to 90 weight %, most preferably from 20 to 80 weight%, with weight % based on the total weight of catalyst product.

In some embodiments, the zeolite(s) for use in the processes describedherein can be exposed to a (post-synthesis) treatment to increase theSi/X₂ framework ratio. Methods to increase the Si/Al₂ ratio of zeolitesare known in the art, and include dealumination of the framework via(hydro)thermal treatment, extraction of framework aluminum with acid,and replacement of framework aluminum with silicon by reaction withsilicon halides or hexafluorosilicates. An exemplary method ofdealumination is described by Remy et al. (J. Phys. Chem. 1996, 100,12440-12447; hereby incorporated by reference).

The zeolites for use in the process described herein preferably areBrønsted acidic zeolites, i.e. having proton donating sites in themicropores. In some embodiments, the zeolite has a Brønsted acid densitybetween 0.05 and 6.5 mmol/g dry weight. When all Al T-sites arecounterbalanced with an acidic proton (as opposed to a cation), theBrønsted acid density can be directly derived from the Si/Al₂ ratio, forexample as discussed in the Handbook of Heterogeneous Catalysis, secondedition, edited by G. Ertl, H. Knözinger. F. Schüth and J. Weitkamp,Wiley 2008.

The zeolites for use in the processes described herein can be obtainedin acidic form (acidic H-form zeolite) or (partly) exchanged with acation other than H⁺. In some embodiments, the acidic H-form zeolitescan be used as such. In some other embodiments, the zeolites for use inthe processes described herein can be exposed to a (post-synthesis)treatment to increase the Brønsted acid density. Brønsted acid sites inzeolites can be readily generated by aqueous ion exchange with anammonium salt, followed by thermal decomposition of the ammonium ionsinside the zeolite. Alternatively, the acid sites may be generated byaqueous ion exchange with the salt of a multivalent metal cation (suchas Mg²⁺, Ca²⁺, La³⁺, or mixed rare-earth cations), followed by thermaldehydration (J. Weitkamp, Solid State Ionics 2000, 131, 175-188; herebyincorporated by reference). In some embodiments, the acidic zeolite hasa Brønsted acid density, between 0.05 and 6.5 mmol/g dry weight.

In some embodiments, the process is performed in the absence of anycatalyst system. Such processes may have up to 25-40% lower conversionand lower yield. However, such processes have the advantage that theycan work at lower capacity and lower cost. Such processes have theadvantage that they can work with higher recirculation. Such processeshave the advantage that separation is easier.

In some embodiments, the process is sometimes performed in the presenceof at least one catalyst system and sometimes performed in the absenceof any catalyst system. The choice may be made depending on a variety offactors, including the composition of the feed. This demonstrates thehigh versatility of such a process.

In some embodiments, at least part of the catalyst system is recovered,preferably together with at least part of the water, preferably througha decantation step. Alternatively, the catalyst system may be recoveredthrough filtration, centrifugal separation or with a hydrocyclone.

In some embodiment, at least part of the catalyst system is present inthe recovered solvent. The catalyst system may be separated from thesolvent by the methods described above.

In some embodiments, the process comprises the step of recovering atleast part of the water, optionally wherein the water comprises at leastpart of the at least one catalyst system.

In some embodiments, the step of recovering at least part of the watercomprises a filtration step preferably membrane filtration, for examplethrough reverse osmosis. In some embodiments, the step of recovering atleast part of the water comprises a distillation step. In someembodiments, the step of recovering at least part of the water comprisesreactive distillation. In some embodiments, the step of recovering atleast part of the water comprises reactive distillation. In someembodiments, the step of recovering at least part of the water comprisesdivided wall column distillation. Distillation plates may be provided ontop of the reactor(s). Fluid heating may be provided by a reboiler,preferably placed at the bottom of the reactor(s).

In some embodiments, the step of recovering thermal energy is performedafter the step of recovering at least part of the water.

The lactic acid may be produced industrially via bacterial fermentationof glucose or sucrose. Microbial fermentation generally results inL-lactic acid, which restricts the potential of PLA, as superiorstereocomplexes PLLA/PDLA require a source of D-lactic acid. In someembodiments, the lactic acid is obtained by bacterial fermentation ofglucose or sucrose.

Alternatively, chemocatalytic transformation of trioses, hexoses,cellulose, or glycerol, may result in lactic acid obtained as a racemicmixture. In some preferred embodiments, the lactic acid is obtained, bychemocatalytic transformation of trioses, hexoses, cellulose, orglycerol.

In some embodiments, the lactic acid comprises L-lactic acid. In somepreferred embodiments, the lactic acid comprises D-lactic acid. In someembodiments, the lactic acid comprises at least 90% by weight, forexample at least 95% by weight, for example at least 98% by weight, forexample at least 99% by weight L-lactic acid.

In some embodiments, the one or more components provided to the at leastone reactor comprises at least 3% by weight of water and at most 95% byweight of water, with % by weight based on the total weight of the oneor more components, preferably at least 5% by weight and at most 50% byweight, with % by weight based on the total weight of the one or morecomponents provided to the at least one reactor, preferably at least 10%by weight and at most 30% by weight, with % by weight based on the totalweight of the one or more components provided to the at least onereactor.

In some embodiments, the one or more components provided to the at leastone reactor at least 90% by weight of solvent, with % by weight based onthe total weight of the one or more components, preferably at least 95%by weight, preferably at least 99.5% by weight.

In some embodiments, the mass flow rate of total quantity of solventprovided to all reactors is at least 4 times to at most 30 times themass of lactic acid provided to all reactors, preferably at least 6times to at most 25 times, preferably at least 9 to at most 20 times.

In some embodiments, the one or more components provided to the at leastone reactor comprises at least 1% by weight of catalyst system and atmost 25% by weight of catalyst system, with % by weight based on thetotal weight of the one or more components, preferably at least 3% byweight and at most 10% by weight, with % by weight based on the totalweight of the one or more components provided to the at least onereactor.

In some embodiments, the one or more components provided to the at leastone reactor comprises at most 1.00% by weight of organic acids otherthan lactic acid, preferably at most 0.10% by weight, preferably at most0.01% by weight, with % by weight based on the total weight of the oneor more components provided to the at least one reactor.

Lactide has two asymmetric carbon atoms so it may be obtained in threestereoisomeric forms: L-L-lactide in which both asymmetric carbon atomspossess the L (or S) configuration; D-D-lactide in which both asymmetriccarbon atoms possess the D (or R) configuration; and meso-lactide(D-L-lactide) in which one asymmetric carbon atom has theL-configuration and the other has the D-configuration.

In some embodiments of the processes described herein, thehydroxycarboxylic acid is L-lactic acid (with an enantiomeric excess ofat least 90%, preferably at least 95%, more preferably at least 98%) andthe corresponding cyclic ester is L-L-lactide.

In some embodiments of the processes described herein, thehydroxycarboxylic acid is D-lactic acid (with an enantiomeric excess ofat least 90%, preferably of at least 95%, more preferably of at least98%) and the corresponding cyclic ester is D-D-lactide.

In some embodiments, the step of recovering at least part of the thermalenergy is performed prior to the step of purifying the recoveredlactide. In some embodiments, the step of recovering at least part ofthe thermal energy is performed prior to the purifying crystallizationstep.

In some embodiments, the step of recovering at least part of the thermalenergy is performed during the step of purifying the recovered lactide.In some embodiments, the step of recovering at least part of the thermalenergy is performed during the purifying crystallization step.

In some embodiments, the step of purifying the recovered lactidecomprises a solvent-solvent extraction step. In some embodiments, thestep of purifying the recovered lactide comprises a filtration step,preferably through a membrane. Such processes have the advantage thathigh quality water is produced. The filtration is preferably forseparation of solid Lactide from the crystallization step. Thisfiltration may be replaced by a crystallization system that separatesthe solids without a filter such as a static crystallizer in whichlactide crystallizes over the walls of the crystallizer. Thepurification step occurs typically after the filtration step (or afterthe crystallization if filtration is not used). The purpose is to removethe trace of solvent present in the separated lactide to produce highpurity Lactide, for example of at least above 99%, preferably of atleast 99.9%, preferably of at least 99.99%. In this step asolvent/solvent extraction may be used but not preferred. Instead avacuum flash can be used to evaporate the solvent in low pressure andtemperatures just below the melting point of Lactide as written in theprevious sections.

In some embodiments, the process has a lactide yield of at least 60%,preferably at least 65%, preferably at least 70%, preferably at least75%, preferably at least 80%, preferably at least 85%.

In some preferred embodiments, the process further comprises the stepof: converting at least part of the recovered lactide into polylacticacid (PLA), preferably PLLA.

The advantages of the present invention are illustrated by the followingexamples.

EXAMPLES Example 1

This example illustrates a process for synthesizing lactide from lacticacid according to a combination of embodiments of the present invention.Reference is made to FIG. 1, composed of FIG. 1A, FIG. 1B, FIG. 1C, andFIG. 1D, which represents a flow diagram of the process of Example 1.

An original feed (100) is provided, wherein the original feed (100)comprises lactic acid (110). When the lactic acid has been obtained froma bio-based feedstock, the original feed (100) usually also compriseslactic acid dimer (120), lactic acid oligomers (130), and water (140).Flow circulation of the components may be performed by one or more pumps(101, 102, 103, 104).

A solvent make-up (150) is provided separately. A catalyst system (160)is present in a closed cycle. A catalyst makeup may be provided toreplace the deactivated catalyst. This catalyst makeup may be addeddirectly to first reactor or be injected into the feed line or beinjected with fresh feed.

The components of the feed (110, 120, 130, 140), and optionally thecatalyst system (160), are provided to a first reactor (710) suitablefor one-step lactide formation. The solvent (150) is provided separatelyto the first reactor (710). The mixture exiting the first reactor isprovided to a second reactor (720) suitable for one-step lactideformation.

The components of the feed (110, 120, 130, 140) are optionally heated bya steam generator (500), which generates heated steam (511) that passesheat onto the components of the feed (110, 120, 130, 140) through a heatexchanger (510). The resulting cooled steam or condensed water (512) maythen be heated again by the steam generator (500)

The solvent is heated, for example by the steam generator (500), whichgenerates heated steam (521) that passes heat onto the components of thesolvent (150) through a heat exchanger (520). The resulting cooled steamor condensed water (522) may then be heated again by the steam generator(500).

The original feed (100) may be combined with water (140), and optionallywith lactic acid oligomers (130) and/or the catalyst system (160), thatwas recovered from the mixtures exiting the first reactor (710) and thesecond reactor (720), to obtain a mixture. This water (140), togetherwith water (140) from the original feed (100), may be used to hydrolyzethe lactic acid oligomers (130) (obtained from either reactor (710, 720)or already present in the original feed (100)) into lactic acid (100)and lactic acid dimer (120) in the recycling pipes. This water (140),together with water (140) from the original feed (100), may also be usedto regenerate the catalyst system (160) (present in a closed cycle) inthe recycling pipes. Optionally a separate recycling reactor (730) isprovided.

Water (140) separation, optionally wherein the water (140) compriseslactic acid oligomers (130) and/or the catalyst system (160), can occurbetween reactors (410), as a decantation step (420) (or alternatively bydistillation or centrifugation) after the second reactor (720). Themixture then is sent to a water separation membrane (430) after mixingwith the original feed (100). These steps result in high quality water(400) and a mixture with adjusted water concentration to be sent to thereactor. The outlet stream from the decantation step containing watermay have some LA and L2A due to possible hydrolysis of the oligomersinside the decanter.

From the mixture exiting the second reactor (720), the water (140),optionally comprising lactic acid oligomers (130) and/or the catalystsystem (160), is separated from the lactide (200) and the solvent (150)in a decantation step (420).

The lactide (200) and solvent (150) are further separated using anoptional refrigeration cycle for lactide crystallization (300). Thecooling may be carried out by refrigeration as in this example, orsimply by cooling water. The refrigeration cycle for lactidecrystallization (300) preferably comprises a compressor (310), heatexchangers for the refrigeration cycle (311, 312), and a valve forrefrigeration cycle (315). Preferably, the lactide crystallizationoccurs in two steps: lactide (200) crystallization in a firstcrystallization reactor (301) (optionally with heat recovery) andlactide (200) crystallization in a second crystallization reactor (302)to finish the crystallization.

The lactide (200) is subsequently separated from the solvent (150) usinga lactide filter (210). Further purification of the lactide (200) may beperformed with a valve for lactide purification (215) and a lactidepurifier (220).

Energy optimization is provided with multiple heat recovery steps(selected temperatures are shown in FIG. 1). A first heat recovery step(610) recovers thermal energy from the lactide (200) and the solvent(150) exiting the second reactor through a heat exchanger (611), andprovides the thermal energy to the solvent (150) through a heatexchanger (612). A second heat recovery step (620) recovers thermalenergy from the water (140), and optionally the lactic acid oligomers(130) and/or catalyst system (160), exiting the first and/or secondreactor through a heat exchanger (621), and provides the thermal energyto the solvent (150) through a heat exchanger (622). A third heatrecovery step (630) recovers thermal energy from the lactide (200) andthe solvent (150) during a crystallization step (301), and provides thethermal energy to the solvent (150) through a heat exchanger (632).

This example permits to produce 7.29 ton/h of lactide and 2.84 ton/h ofwater with an inlet feed flow rate of 10.12 ton/h.

The inlet flow comprises 90% by weight of lactic acid equivalents andapparent 10% by weight of water. The lactic acid equivalents itself,comprises approximately 70% by weight of lactic acid, 23% by weight oflactic acid dimers and 7% by weight of lactic acid trimers, the % byweight based on the total weight of the lactic acid equivalents. Whererelevant, the amounts of heat that are to be added to the process or areliberated during the process are mentioned in FIG. 1 (as Q= . . . ), theunit used for these amounts of heat is kJ/sec. During the twocrystallization steps, 2200 kWh can be recovered, which corresponds toabout 20% of the total recovered energy during the process. This alsorequires 50% less cooling capacity in the refrigeration cycle.

Example 2

FIG. 2 illustrates a semi-batch catalyst injection system which may beused in the present invention.

The inlet stream of the water separation unit typically contains a largecontent of catalysts (up to 30 wt %). This high catalyst content may beharmful for the membrane or filters used in the water separationsection. In this case, a catalyst separation unit may be installedupstream of this unit to protect filters/membranes. In this case, ahydro-cyclone or a centrifugal separator may be used to separatecatalyst and re-inject it into the reactor inlet stream or probablyre-inject directly into the reactor. Direct catalyst injection into thereactor has the advantage of being able to use normal pumps on thereactor inlet stream.

The catalyst injection into the reactor may require a dedicated systemparticularly in the case of a pressurized reactor. A possible method isuse of semi-batch catalyst injection systems similar to theconfiguration proposed in FIG. 2 This system operates in three phases:Storage: during which valve (22) is closed and the system receivescatalysts from stream (1) from the centrifugal separator—Pressurization:in this phase the catalyst inlet is stopped by closing valve (21) andthe system is put under pressure via gas inlet line (3)—Discharge:catalysts are discharged into the reactor during this phase by partiallyopening the valve (22).

Two or three catalyst injection system can be installed for each reactordepending on the process configuration.

Example 3

The role of solvent is to avoid direct contact between water andproduced lactide. However, water presence may have positive impact viahydrolysis of oligomers. In case the solvent has a good solubility forlactide and little solubility for water, it should be less harmful forlactide in the reactor. However, water presence may cause lactidehydrolysis if solvent does not dissolve well produced lactide. Thisdepends on the overall reaction and dissolution mechanism.

Some alternative designs are proposed in this example to add adistillation option directly into the reactor for in situ waterseparation. Various kinds of reactive distillation reactors may be usedin this case. FIG. 3 shows some possible configurations. Depending onthe nature of the solvent, other kind of designs may be used. Someadvanced distillation systems such as divided wall column may be used toproduce a concentrated lactide outlet stream inside the reactor to easethe downstream separation steps. The energy consumption may be reducedby use of heat integration to recover at least a part of the evaporationenergy which is inherent to the distillation.

Example 4

This example illustrates a process for synthesizing lactide from lacticacid according to a combination of embodiments of the present invention.Reference is made to FIG. 4, which represents a flow diagram of theprocess of Example 4. All the thermal energy is added via the solventstream, further reducing the CAPEX compared to Example 1.

An original feed (100) is provided, wherein the original feed (100)comprises lactic acid (110). When the lactic acid has been obtained froma bio-based feedstock, the original feed (100) usually also compriseslactic acid dimer (120), lactic acid oligomers (130), and water (140).Flow circulation of the components may be performed by one or more pumps(101, 102, 103, 104).

A solvent make-up (150) is provided separately. A catalyst system (160)is present in a closed cycle. A catalyst makeup may be provided toreplace the deactivated catalyst. This catalyst makeup may be addeddirectly to first reactor or be injected into the feed line or beinjected with fresh feed.

The components of the feed (110, 120, 130, 140), and optionally thecatalyst system (160), are provided to a first reactor (710) suitablefor one-step lactide formation. The solvent (150) is provided separatelyto the first reactor (710). The mixture exiting the first reactor isprovided to a second reactor (720) suitable for one-step lactideformation.

The solvent is heated, for example by the steam generator (500), whichgenerates heated steam (521) that passes heat onto the components of thesolvent (150) through a heat exchanger (520). The resulting cooled steamor condensed water (522) may then be heated again by the steam generator(500).

The original feed (100) may be combined with water (140), and optionallywith lactic acid oligomers (130) and/or the catalyst system (160), thatwas recovered from the mixtures exiting the second reactor (720), toobtain a mixture. This water (140), together with water (140) from theoriginal feed (100), may be used to hydrolyze the lactic acid oligomers(130) (obtained from either reactor (710, 720) or already present in theoriginal feed (100)) into lactic acid (100) and lactic acid dimer (120)in the recycling pipes. This water (140), together with water (140) fromthe original feed (100), may also be used to regenerate the catalystsystem (160) (present in a closed cycle) in the recycling pipes.Optionally a separate recycling reactor (730) is provided.

Water (140) separation, optionally wherein the water (140) compriseslactic acid oligomers (130) and/or the catalyst system (160), may beperformed as a decantation step (420) (or alternatively by distillationor centrifugation) after the second reactor (720). The mixture then issent to a water separation membrane (430) after mixing with the originalfeed (100) and optionally passing through the recycling reactor (730).These steps result in high quality water (400) and a mixture withadjusted water concentration to be sent to the reactor. The outletstream from the decantation step containing water may have some LA andL2A due to possible hydrolysis of the oligomers inside the decanter.

From the mixture exiting the second reactor (720), the water (140),optionally comprising lactic acid oligomers (130) and/or the catalystsystem (160), is separated from the lactide (200) and the solvent (150)in a decantation step (420).

The lactide (200) and solvent (150) are further separated using anoptional refrigeration cycle for lactide crystallization (300). Thecooling may be carried out by refrigeration as in this example, orsimply by cooling water. The refrigeration cycle for lactidecrystallization (300) preferably comprises a compressor (310), heatexchangers for the refrigeration cycle (311, 312), and a valve forrefrigeration cycle (315). Preferably, the lactide crystallizationoccurs in two steps: lactide (200) crystallization in a firstcrystallization reactor (301) (optionally with heat recovery) andlactide (200) crystallization in a second crystallization reactor (302)to finish the crystallization.

The lactide (200) is subsequently separated from the solvent (150) usinga lactide filter (210). Further purification of the lactide (200) may beperformed with a valve for lactide purification (215) and a lactidepurifier (220).

Energy optimization is provided with multiple heat recovery steps(selected temperatures are shown in FIG. 4). A first heat recovery step(610) recovers thermal energy from the lactide (200) and the solvent(150) exiting the second reactor through a heat exchanger (611), andprovides the thermal energy to the solvent (150) through a heatexchanger (612). A second heat recovery step (620) recovers thermalenergy from the water (140), and optionally the lactic acid oligomers(130) and/or catalyst system (160), exiting the first and/or secondreactor through a heat exchanger (621), and provides the thermal energyto the solvent (150) through a heat exchanger (622).

Compared to Example 5, the above feed (100) is injected into theseparated water stream from the decantation step (420). Accordingly, thefeed (100) is heated up to 96° C. due to direct mixing without use ofheat exchanger. This causes the lactic acid oligomers that are presentin the feed to hydrolyze to LA and L2A. Also, the feed has to passthrough water separation membrane (430) reducing the water content thatis fed into the reactor. Therefore, the recirculation rate is reduced byabout 20%. The heating rate is considerably reduced due to substitutionof the energy intensive distillation unit. Due to heat integration andsubstitution of the distillation unit, the total heat required in thisexample is about 25% of the requirement in the Example 5. In addition,the maximum temperature of the streams containing lactide (200) in thisexample is limited to 168° C. which permits avoiding thermal degradationof LD.

Example 5

This example illustrates a process for synthesizing lactide from lacticacid. Reference is made to FIG. 5, which represents a flow diagram ofthe process of Example 5.

An original feed (1100) is provided, wherein the original feed (1100)comprises about 10% by weight of water (1140) and about 90% by weightlactic acid equivalent, itself comprising lactic acid (1110), lacticacid dimer (1120), lactic acid oligomers (1130). Flow circulation of thecomponents is be performed by one or more pumps (1101, 1102, 1103,1104). A catalyst system (1160) is present in a closed cycle.

The components of the feed (1110, 1120, 1130, 1140), the catalyst system(1160), an d the solvent (1150) are mixed and heated up in a first heatexchanger (1691) before these components enter the reactor (1740)suitable for one-step lactide formation. After a residence time of 1hour in the reactor (1740), the reaction products leave the reactor(1740) and the solids (comprising the catalyst (1160) are separated fromthe rest of the reaction mixture by centrifuge (1440). Said solids aresent to a recycling reactor (1730). The liquid fraction is fed into adistillation column (1450), wherein the heavy fraction is separated fromthe light fraction. The light fraction comprises solvent (1150), (decanein this case) that form an azeotrope with water (1140). This lightfraction is send through a heat exchanger (1693) to be cooled down andwater (1400) is separated from light fraction. The heavy fraction doescomprise lactide (1200), lactic acid dimer (1120) and lactic acidoligomer (1130).

The heavy fraction is passed through a heat exchanger (1692) to cool itdown, before it is crystallized in crystallization reactor (1303) andfiltered by filter (1210). The filtrate is reused as solvent (1150) andcarries the lactic acid dimers (1120) and lactic acid oligomers (1130)back into the reactor. The solid fraction is further purified in lactidepurifier (1220) to yield the desired lactide (1200). An optionalregeneration step may be added into the solvent and feed stream toregenerate lactic acid oligomers (1130) and lactic acid dimers (1120) byhydrolysis with water before mixing with catalyst stream.

This example permits to produce 7.18 ton/h of lactide and 2.83 ton/h ofwater with an inlet feed flow rate of 10.12 ton/h. Where relevant, theamounts of heat that are to be added to the process or are liberatedduring the process are mentioned in FIG. 5 (as Q= . . . ), wherein QCstands for the “cooling heat rate” and QR stands for the reboiler heatrate. The unit used for these amounts of heat is kJ/sec.

The distillation column in this example requires large amounts ofenergy, namely 30 MJ/s. Not all the lactic acid oligomers are beingremoved from the heavy fraction. This requires extra efforts during thepurification of the lactide and it makes the recirculation system of thelight fraction less effective to turn the oligomers into useful startingmaterials for the lactide formation. Further, there is a reboiler neededthat warms up the heavy fraction comprising the lactide (1200) to about288° C. This causes partial degradation of the formed lactide (1200),negatively influencing the yield of the overall process. All this canlead to about 20% higher energy consumption than in the process ofExample 1.

Another disadvantage of this set up is that the feed is added justbefore the reactor, whereas the feed in Example 1 and Example 4 is addedin the water recycling loop. The feed in example 1 and 4 has to passthrough recycling reactor (730) before it enters the reactor (710). Thishas the advantage that even before the feed enters the reaction, theoligomers that are present in the feed are getting broken down to LA orL2A, and enter the reactor (710) as useful starting material. If thefeed is added directly to the reactor, the oligomers cannot take part inthe reaction and are only be able to be processed after they passedthrough a cracking step. Overall this lowers the efficiency of theoverall lactide formation.

Example 6

The catalyst leaves the reactor with a certain amount of lactic acidoligomers adhering on the surface of the catalyst. FIG. 6 showsthermogravimetric analysis (TGA) of used catalyst particles after noregeneration, after 15 minutes of regeneration and after 30 minutes ofregeneration in water at 45° C. The first graph (0 h) of the figureshows the TGA results carry out on a non-generated catalyst comprisingoligomers on the surface. Three peaks can be distinguished in this case,the first peak (around 100° C.) corresponds the removal of water, thesecond peak (between 200° C. and 300° C. corresponds to the removal ofsolvent, and the third peak (between 300° C. and 370° C. corresponds tothe removal of oligomers from the catalyst surface. The second graph (15min) shows the TGA results for the same catalyst comprising oligomers onthe surface after 15 min contact with water of 45° C. to hydrolyzeoligomers and regenerate catalyst. In this case, the third peak relatedto the oligomer does not appear, showing that the contact with water hascompletely removed oligomers and regenerated the catalyst. The thirdgraph show the TGA results for the same catalyst comprising oligomers onthe surface after contact with water of 45° C. for 30 min. The TGAresults are approximately identical to the TGA results after 15 minwater exposure. These results show that catalyst can be effectivelyregenerated by water in a contact time below 15 min.

Contact time may be reduced if the water temperature is higher than 45°C. as shown in examples 1 and 4 where the separated water and catalyststream has a temperature of 170° C. in the decanter with high watercontent available.

A technique that is often used in the art to regenerate the catalyst iscombustion of the oligomers stuck to the catalyst surface (cokedcatalyst), where the accumulated oligomer is burned from the catalystsurface. However this technique requires extra energy for the combustionand puts and shortens the catalyst lifespan.

The invention claimed is:
 1. A process for synthesizing lactide,comprising the steps of: adding thermal energy to at least one of one ormore components; providing the one or more components comprising lacticacid and at least one aromatic solvent; converting at least part of thelactic acid into lactide and water; recovering at least part of thelactide; recovering at least part of the at least one aromatic solvent;recovering at least part of the thermal energy, wherein at least part ofthe recovered thermal energy is recovered from the recovered aromaticsolvent; and adding the recovered thermal energy to at least one of theone or more components, wherein the steps of: recovering at least partof the thermal energy, wherein at least part of the recovered thermalenergy is recovered from the recovered aromatic solvent; and adding therecovered thermal energy to at least one of the one or more components;are performed with a heat exchanger.
 2. The process according to claim1, wherein the process is an industrial process for synthesizinglactide, and wherein the step of converting at least part of the lacticacid into lactide and water is performed in one step.
 3. The processaccording to claim 1, comprising the step of: recovering at least partof the water; wherein at least part of the recovered thermal energy isrecovered from the recovered water.
 4. The process according to claim 1,wherein at least part of the recovered thermal energy is recovered fromthe recovered lactide.
 5. The process to according to claim 1, whereinthe step of recovering at least part of the lactide comprises a firstcrystallization step and a second crystallization step.
 6. The processaccording to claim 5, wherein the first crystallization step and thesecond crystallization step are each independently cooled.
 7. Theprocess according to claim 5, wherein the step of recovering at leastpart of the thermal energy is performed during the first crystallizationstep.
 8. The process according to claim 5, wherein the step ofrecovering at least part of the thermal energy is performed during thesecond crystallization step.
 9. The process according to claim 1,wherein at least part of the recovered thermal energy is added to thelactic acid.
 10. The process according to claim 1, wherein the one ormore components comprise at least one aromatic solvent, and wherein atleast part of the recovered thermal energy is added to the aromaticsolvent.
 11. The process according to claim 1, wherein at least part ofthe recovered thermal energy is recovered from the recovered water,wherein at least part of the recovered thermal energy is recovered fromthe recovered aromatic solvent, wherein at least part of the recoveredthermal energy is recovered from the recovered lactide, and wherein atleast part of the recovered thermal energy is added to the aromaticsolvent.
 12. The process according to claim 1, comprising the steps of:adding thermal energy to at least one aromatic solvent; providing one ormore components to at least one reactor, the one or more componentscomprising lactic acid and the at least one aromatic solvent; convertingat least part of the lactic acid into lactide and water; and recoveringat least part of the lactide; wherein the step of adding thermal energyto the at least one aromatic solvent is performed prior to the step ofadding the at least one aromatic solvent to the at least one reactor;and wherein the at least one aromatic solvent is provided in the atleast one reactor independently from the lactic acid by a separate entryinto the at least one reactor.
 13. The process according to claim 1,comprising the steps of: providing one or more components to at leastone reactor, the one or more components comprising lactic acid;converting at least part of the lactic acid into lactide and water andinto lactic acid oligomers; recovering at least part of the lactide;recovering at least part of the water and at least part of the lacticacid oligomers; adding a feed, optionally comprising lactic acidoligomers, and optionally comprising water, to the recovered water andthe recovered lactic acid oligomers, and mixing the feed with therecovered water and the recovered lactic acid oligomers to form amixture; converting at least part of the lactic acid oligomers in themixture into lactic acid and into lactic acid dimer; and removing atleast part of the water from the mixture; whereby at least part of theremainder of the mixture is provided as one of the one or morecomponents that are provided to the at least one reactor.
 14. Theprocess according to claim 1, comprising the steps of: providing one ormore components to at least one reactor, the one or more componentscomprising lactic acid; converting at least part of the lactic acid intolactide and water; recovering at least part of the lactide; andrecovering at least part of the water; wherein the step of recovering atleast part of the water comprises a decantation step, with the provisothat the step of recovering at least part of the water does not comprisean azeotropic distillation step.